The wait for the most expensive buffet in Disney is a long one so it does effect other people that want to be seated.
No
I dont believe so. Reservations arent for a particular table. They just may sit you at a smaller table since you'll only have three.
They'd like you to let them know 24 hrs prior, but the same thing happened to us last week; we had booked 7, but 2 canceled and the app wouldn't let me adjust it so I just told them when we arrived and it was okay.
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