Destination wedding with a baby?

My brother and his fiance want to have a destination wedding in Europe. We live in the US. I am married with 3 kids and a baby on the way. He wants only immediate family to attend and all children. When the wedding date arises, I will have a 4 month old baby. The idea of traveling 8 hours on a flight with an infant is severely overwhelming. Also the amount of items I'd need...car seat, stroller, pack n play, etc. Also, it's the week after my other kids start school for the year in the fall. I'm having a really hard time being on board with this plan of theirs. Also, as a family of 6, we have to think about our financial situation as well as obtaining time off of work after I will have just taken 10 weeks or so of maternity leave. I just don't see this as fathomable and I'm sad about it. My brother doesn't seem to understand the hardship that this is from many angles. Someone help me in navigating this!