My SO's brother is getting married in five months. I am seriously considering not going (and staying home with our LOs)

1. I am on track to be 31 weeks pregnant. No history of preterm labor, but both births were assisted and both were born with heart defects (so I will most likely be considered high risk)
2. DS will be 16 months, DD will be 4. I can't find any round trip flights where we can choose our seats or that have two groups of two next to each other. DS would be a very uncomfortable lap infant.
3. There are no direct flights. 7 hours there and 8 back. Five of which are in the air.
4. SO has never met his future SIL, nor have their parents.
5. Parents and SO both found out about the wedding date from Facebook
6. The couple is having an engagement party the weekend after his parents are visiting for a week and a half

So basically, I am afraid of going into labor on the other side of the country to a sick baby. There is tons of family drama. Flights are filling up really quickly already so I'd really like to make the decision now. No matter what SO is going, but he left it up for discussion as to whether the kids and I go.

Would you feel weird about not going?