To me, the best part about a large extended family trip is the ability to divide and conquer, not forced togetherness for 10+ people. Some kids want to ride the big thrill rides, even if it means waiting in line? A patient, thrill ride loving adult can chair that one. Some of the kids are tired of the park and want to go back to the hotel/Airbnb? A Disney park hating adult can run them back. Some of the kids want pizza, some want burgers? No problem. And bonus- trading off all the kids for adult time! It sounds like when the OP was able to take advantage of this, the trip went much better. I would totally do a big group trip, but definitely with the idea that we will be splitting into smaller groups each day so everyone gets to do what they want. And I probably wouldn't even bother trying to organize more than one sit down meal for the whole group- the entire trip. Or if I did, it would be off property. But I understand doing this would require a lot of cooperation between adults, and maybe when a grandparent is bankrolling the whole thing, the other adults feel like they can't really speak up about what they'd rather do. (Not that this was a problem for the SIL-yikes).