Anonymous wrote:OP here - interesting to see the range of responses!
We have a toddler, have flown with him multiple times, and are definitely aware of how hard plane travel becomes around the 1 year mark. I wish we could put off plane travel indefinitely because we’ve had some hellish travel experiences with our older son, but unfortunately we can’t get away with insisting that people come to visit us instead of us going to them for years on end. We’ll probably travel to see these same relatives for Thanksgiving. Baby will be 7 months old then and will have gotten Tdap, flu, Covid shots. I don’t think it’s unreasonable to wait until then (especially because, as I said earlier, these relatives have already met the baby and will probably come back for another visit sometime in the late summer or early fall).
It sounds like you want to hold off, so you should hold off. You can use the pediatrician's advice as an excuse if they are very critical, but I don't think you should have to say that -- you should simply be able to say that you don't feel ready to fly with the new baby yet. And the fact that you have an older child who is at what many consider to be the worse age for flying would just make me feel even more confident in that decision.
Also, it sounds like you have the kind of relatives who are very insistent about you traveling, and like to dismiss any potential obstacles as unimportant. In that case, I'd get used to saying no now. Because these same people will be demanding that you travel even when it means the kids miss school or activities, or even if they are sick or the trip will be too disruptive to family schedules. My parents are this way and I've had to learn to just say no and ignore their wheedling. The more you give in, the more they think they can get away with. You have to start setting these boundaries now or it just gets worse as the kids get older.