I know it is super early to be worrying about this. But we have told our immediate family members and they have all been offering to come stay with us. We will see if it actually happens, but all of the offers are starting to freak me out. I know we will need help. But eventually we have to figure it out on our own right? And these people all want to come "live with us" to help (we live away from family.) Our house is only 1000 sq feet and I feel like after the first couple weeks, I will just feel cramped and annoyed.
So far my mother, MIL, SIL, and sister are all offering to come stay for weeks.
Am I going to need all of this?
Re: How much help is too much?
Yes, you'll need it. But with that said.
My advice is to start by making a chore list to define what help is. Things such as dishes, meals, grocery store runs, watching the kids while you get a shower, cleaning, etc. This will free you up to get use to two babies at once.
Make sure to make a list of what is off limits. If you are sensitive about people touching or cleaning specific things, make that clear in advance. For example, my frying pan is my best friend when it comes to being in the kitchen. But after my sister washed it and "put it away," I couldn't find it for a whole month. That bent me out of shape but it is my fault for not telling her how important it was.
Do they live close enough that they could drive there so that if you find that you don't need help or need more help, that they can leave at any time?
If you don't already have one, look into getting an aerobed for guests so it is something that you can deflate or move out of the way if need be.
Personally, I wouldn't have been able to deal with constant house guests.
Are you planning on BFing? If so, much of the responsibility will fall on you anyway.
I didn't have any help other than my husband and it worked out well. We were able to establish our own systems, etc. without other people taking control. Even though some family offered to help, the things I needed help with (household chores) wouldn't get done by them because they'd rather hold the babies, etc.
I think it's wonderful to have help if you want it, but I personally wouldn't be able to deal with live in help other than my DH.
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My next question should be - how do you say no?
I definately think my mom will come live with us for a couple weeks. Because she knows me and what is/is not too much. But I am not really that close to MIL and SIL and would feel like I have to entertain them if they came to stay. And I think that is what is freaking me out. I don't want to hurt their feelings. (They live 2.5 hours away, so it's not like they can just "stop by")
I have a toddler and will have newborn twins too and I generally like having alot of help around but that seems like ALOT of people to me. Figure out who is likely to be most helpful to you and invite one or two people to help. One can help with your toddler, take them out of the house, keep them busy, etc. The other can help you manage the house and twins. You might have a c-section so you might need some help because of that and it's alot to manage a toddler, twins and a household. Figure out who can help you with cooking, cleaning, etc. and that person should be your second helper.
As for saying no to MIL and SIL, I'd talk to your husband about it and, ideally, he should do that since it's his family. I really think you should say something like you are happy to have them come visit (maybe offer to put them up at a hotel if you can that way they won't stay with you but they can still see the babies) but that you feel overwhelmed with everything going on, you don't have a ton of space, and that you're just having your mom stay.
It sounds like having your mom around will be ok - I found my mom was very helpful..and if she was doing something annoying/out of line/etc. I had no problem telling her to stop/leave me alone/whatever...
My ILs were in town for the first 10 days we were home with the girls since it was also my SILs wedding...I told everyone well in advance that there was no way in he!! anyone was staying with us...(I was nice about it though...and let DH share the news 1st with his family)...it was overwhelming enough having them come over every morning and leave every night....if you are uncomfortable with the idea...have your dh tell them now...it is not worth your sanity to not put your foot down...good luck!
How to say no is simple.........I would say that doctors advised limited exposure in the beginning. How can they argue with a doctor right?
Honestly.....I think one person other then DH is enough. More then that seems completely overwhelming to me. And if you do have one person there I would say their job is to help with DS#1, meals and cleaning. If they are not ok with that then have someone else. I would out yourself and the babies in your room and stay there. Have DS come in a visit but really just give yourself time to bond with the babies and get used to having them there. My MIL offered to come help but I KNOW she would want to do things for the babies and not do what really needs done so I went without. DH was home with me for 10 days after the hospital before having to go back to work and I did it on my own after that.
As you have said you are still very early on in the pregnancy. Tell them that while you appreciate the offer that you think in the very begning when the babies come home that you think it is important you have time as a family without house guest that stay over night.
I had my MIL say with me for two months, trust me even though I was terrified of my first day alone with them I was more than ready for her to leave. Having help is great, epically if you have a c-section, but having company for that long is very stressful and can at times cause more problems.
I agree with the chore chart, if you do let someone come sit them down before hand and let them know what you expect and what would and what would not be help
Word for word ditto!
I totally agree with tiki's post.
A few more thoughts as I'm living through this now 4 weeks post partum. Decide NOW what type of "help" you need and be honest with people about it. You will need/want help in the beginning, especially the first 2 weeks IMO.
My mom took a couple of weeks off and it has been great as she comes during the week and helps with the the twins AND occasionally cooks meals and does some household chores. However, she lives 30 minutes away so she goes home when my DH comes home from work and she doesn't come on weekends. Originally she planned on "living" with us and sleeping over 24/7, but I knew that was too much togetherness for me, so I told her to just come during the day.
My MIL just likes to come and dote over the twins. While nice, this is all she'll do and she'll spend the ENTIRE weekend at our house and not lift a finger unless it's to play with the kids. She has a week off in February and if she asks I'm going to tell her that she cannot stay over with us the whole week to be entertained.
I would definitely space out all visitors and be honest with yourself about how much togetherness you can handle. I don't know that I'd want people living at my house for more than a few days at a time, but that's just me. Let people know that you cannot and will not entertain them, especially if you have a c-section.
I dealt with this from my MIL with a singleton. Before Emerson was even born, she was telling me what to do. Um, I'm in my mid thirties. Don't tell me how to run my house!
Anyway, I politely told her my mom would be here to help but, I appreciated her offer. Don't feel bad. She'll be able to help with her daughter if she hasn't already.
In my situation my mom offered to stay for a week and longer if she was needed- my DH did not take any time off work (he has Fri, Sat and Sun off) every week so I would of needed help to get established as these were my first and I was planning on BFding.
Once the babies were born my mom did in fact stay with us for a week and a half to two weeks, but not during weekends because DH was off and it gave us some time as a family, her help IMO was a lifesaver! She helped out day/night and helped me and the babies to get established on a routine.
After that time I decided that I was "ready/willing" to be on my own and see how much I could do and have been since.
Once the babies are here you'll see what works best for you 
It really depends on what YOU want.
My mom stayed with us for at least a few days after each of our boys were born. Nice to have our food cooked for us, etc. but I'm also the type that doesn't relax enough when guests are over. When our 1st was born it was nice to have the emotional support. She didn't stay this time and we were fine. It was actually nice to just have the house to ourselves!
A few months ago we lined up 2 girls from our local college to help out a few days a week and after our 1st day of it I don't think it's worth the money : ( The girl just held one of the sleeping girls while I chased around after our 1-year-old and drove our 3-year-old to preschool. Now I think I'm just going to pile all four kids in the car to drive him instead. Our girls are almost 4 weeks old and all they've been doing is eating and sleeping anyway!
The one thing that has been really nice is that people from our church have been bringing meals twice a week. Much appreciated!!
I'm glad you posted this, I've been thinking about the same thing recently.
I overheard my husband on the phone with his mom, and he asked her to come and stay for two weeks! I shrieked, literally shrieked, "Nooo!" Then to cover my embarrassment I made up the 4 day rule, on the spot. No one stays longer than 4 days. I don't think I could stand my own mother longer than 4 days, j/k.
Right now, I'm working on scheduling all of these helpers. I know I want my mom there first. I'm going to try to schedule in-laws to be there when my husband is there (he can be my buffer). And I am going to make a list of things I will need help with, laundry, dishes, suppers, floors, etc. I think that will be the hardest part, making a list. I am so used to playing hostess when people come over and trying to have everything just so when they arrive...it's going to be hard to actually delegate. So I want to make it clear now.
The only person I think I would want to remain exempt from the 4 day rule is my BFF, and I think she is coming last so I can vent when she gets there, haha. Good luck!!
I agree w/ pp about lists for people. Like you said, your mom knows how you are, but the IL's aren't on the same level so they'll need some guidence about what you want. But, you'll know when its too much. I remember one day when the kids were about a month old when my mom was here and then all of a sudden MIL, FIL and both SIL's showed up. FIL was trying to be helpful and fix our dryer and the rest of them were trying to help too, but it was so overwhelming. I looked at my mom and told her I was going to take a nap (we were sleeping in the kids room) She knew why I was going. I just shut the door and turned off the baby moniter. Good Luck!