My older kids are 7,7 and 5. Obviously when little sister was born, my twins were too young to really know what was going on. I had a miscarriage this March, and for that baby, we had told them when we told other family at like 6 weeks, but only because we were at Disneyworld with the whole family and it affected things there. They were really excited and very caring and loving. Untelling them was awful. They have asked, multiple times when I will have another baby.
Now that I am pregnant again, I don't know when to tell them, or how. We had an u/s last week at 6w1d and will have another next Friday. If everything is going well, I think I will want to tell them then. Realistically I know that anything can happen any time. I am just not sure how to do it. I also am worrying that if I get much sicker with symptoms they are going to be concerned that something is wrong with me. Since it is summer, we are all together all day everyday.
Sorry to ramble, just wondered what everyone else is doing with older kids, especially if you have had a loss.
Married - 7/29/06
Ben and Maggie - 4/10/09
Mia - 6/16/11
Surprise! due 2/23/17

Re: If you have older kids - when/how to tell?
TTC since January 2016
BFP - 3/12/16 - MC 4/5/16
BFP - 6/11/16
Ben and Maggie - 4/10/09
Mia - 6/16/11
Surprise! due 2/23/17
Rainbow baby after 3 losses
Due February, 2017
Like what was previously mentioned I think there is a thread that has some info on this, but that was a while ago and I didn't tell my kids at the time, but I have told them now. My kiddos are 9 and 7. We just told them hey you guys are gonna have a baby brother or baby sister. However I have never been exposed to loss from any family or friends as an adult. (My aunt had a loss but I was a baby) this is my first exposure to all that (on this site) and I got really nervous about the risk of loss, so I'm not sure if I did the best thing or not but I gently explained to my kids that there is a possibility of the baby not making it. They of course asked a million questions but I felt like I'd rather them know it could happen. If I would have the misfortune of a loss, I can tell my kids something like remember mommy told you sometimes it doesn't work out... I hope it doesn't come to that but I feel that them knowing it could happen will make them more accepting if it did happen. Plus once my kids were told I could relax and explain to them why I was always feeling sick and napping. I'm not sure if this is of any use to you or not, but that's what happened when we told our kids.
::TW::
When we had to tell them I lost the baby it was awful. My oldest daughter cried and was really sad for a few days. My son, who has anxiety, was just really worried about all the details, and if we had to give the stuffed animal back that we bought for the baby in Disney world. We basically just explained that the baby stopped growing and was too tiny to be born. They have stopped asking if we are going to have another, but my daughter I guess had a whole conversation with my mom yesterday about "when Mommy has a baby, we will share a room, and she can have half my closet". My mom thought she knew what was going on, but I think it was just wishful thinking.
Ben and Maggie - 4/10/09
Mia - 6/16/11
Surprise! due 2/23/17
Diagnosed with PCOS March '10 - Started 1000mg of Metformin

After 3 unsuccessful Clomid cycles, FSH+Ovidril+IUI+Progesterone=BFP!
Time to make Emilie a big sister!
May '16 2.0: Letrozole+FSH+Menopur+Ovidril+IUI+Progesterone=BFP! first beta-45.44, second beta-148
As I'm sure you know, there's no "right" time, so I'm sure you'll find the best one for you and your fam. Best of luck to you!
By the time I was pregnant with my daughter my sons were old enough to just tell them. I waited until about 8 or 9 weeks. They were teenagers. Should we ever have another I will tell my daughter when I am showing.
For this my sons knew a year before we transferred because of the situation. My daughter will know closer to the end. (We have books to help explain-The kangaroo pouch etc)
Jack gained his wings on 09/02/2016.
Kali gained her wings on 07/28/2015.
They will be forever missed.
I think when we tell our kids it will have to be with some explantation of caution. But like you mentioned, I suspect on some level, my kids already know, at least my oldest daughter.
Ben and Maggie - 4/10/09
Mia - 6/16/11
Surprise! due 2/23/17
We're supposed to go Disneyland at 10+2, so I was going to tell her this week. Now my husband's sprained his ankle (both low and high). He can't go to DL and may not be capable of taking care of himself so I can go without him.
If we cancel the DL trip, I'll probably wait to tell her until I get the results of the NIPT back around 11 weeks. If we go to DL, I'll tell her a bit earlier.
She was very excited but when I explained how long she had to wait she calmed down. She just keeps saying she hopes its a sister.