Hey STMs! Wondering what life was like for you when you had your first and they were about 3 months? My husband has planned this big weekend when the baby will be about 3 months if he delivers close to his EDD

He invited his parents and his three siblings, which includes their 3 spouses and total of 4 kids (2 very young and 2 teenagers). We moved to a new state a little over a year ago and only his mom has been here, so he wanted everyone to come to spend some time with our new LO but also to see where we live. So the plan is to be pretty active doing lots of touristy things, kid friendly activities like the zoo, spending time at our house, etc. Normally I would really be so excited. I get along really well with his family and love seeing them. But the whole idea overwhelms me. I have no idea what it's like to be a new parent, but I feel like 3 months is MAYBE when I would start feeling like "Hey - I can do this!" but with me and LO at home, not entertaining 12 additional people!?!? It makes me feel like hyperventilating every time I think about it. Especially when I think about all the work that goes into getting your house ready to have people over who haven't seen it before and would be taking "the tour" and looking around, etc. It's gotta be spotless!!! He said he "thinks" everyone would be staying in a hotel, because who wants to stay with people who have a three month old, and we only have 2 extra bedrooms anyway, but he also said if someone asked about staying that of course we would say yes. That makes me even more nervous !! AHHH!!
Maybe I am just freaking out because everything right now is so unexpected? Do you think you had a handle on things and could manage 3-4 days of a big family event that you and SO hosted with your 3 month old? Too overwhelming? Not a big deal?! Am I crazy for being crazy?! LOL
Re: STMs - Life @ 3 months?
Everyone will want to be near baby and probably help out in that respect.
I think you'll be okay. At 3 months I was back at work and we were also about to make a cross-country move, so our house was in chaos, but we were fine.
You can always back out of certain activities and outings if you're feeling tired or overwhelmed (use the baby or "the doctor said..." as an excuse). Just focus on yourself and the baby and let your family entertain themselves. 
ETA: I'd also point out to him that you definitely don't have room for everyone, so maybe agree that if his parents ask they can stay with you, but his siblings should get a heads-up that they definitely need to get a hotel. I already had the "your dad needs to get a hotel" convo with my wife--I wanted NO confusion on that point!
Every baby is different but it would be no big deal to me as long as the family knew that nap times were going to be enforced and the house would need to be quiet and if you are BFing that a) boobs would be out or b) make sure you have an off limits space for that time that's comfortable for you.
With regard to your specific situation, I agree with some things PP's have mentioned, including talking to DH about expectations. Perhaps have him let the grandparents know that if they would like to stay at your place they are welcome, but the siblings and cousins will need to get a hotel. Also, since it is your DH that is planning this whole endeavor, let him know you will absolutely expect him to clean and ready the place for the family to arrive. And be clear that if you or the baby are getting too overwhelmed with the activities, number of people trying to hold the baby, etc, that you can and will bow out of certain outings/take baby to a private quiet room/call it a night whenever you feel it's needed, and that this will happen without guilt, or pouting, or any of that family stuff that sometimes occurs.
Overall though, I'd say it should be a good time for you and your husbands family. It's also a bonus that everyone coming has kids of their own. Whether they are grown or are toddlers, these people have been where you are. And parenting styles change, new information helps us better care for our kids, but that feeling of BEING a parent is something that they will all be able to celebrate and sympathize with.
Been married since 2009.
Unicornuate Uterus (yes I menstruate glitter)
Several MCs
DD born 2013 (our miracle "you can't have babies" baby!)
You're going to have a blast!
Also, totes hire someone to clean the house. Worth it.