I don't know where you'll be staying, but I'm guessing ASMu since you'll be there for Magic Music Days. I'd pick the easiest one to get to with minimal transfers. Trying to keep track of all those kids, even with chaperones, you'll probably not all get on the same bus. So, if you can just take one bus and then all meet up again, would be the easiest, instead of having to transfer. I picked Cryatal Palace, since it's my favorite character breakfast and located at the MK, which would be easy to get to from ASMu. Just remember to call group dining to make your ressies!!