We went 2 years ago this coming Thanksgiving with our 3 year old. AMEX confirmed we had early seating, got onboard to be told we had late seating. Was not good at all for the daughter. The only good thing was that you got to go to the early show - which the kids shouldn't miss. If we did have early seating, then she would have been sleeping during the show.
But, there are plenty of things for the kids to eat onboard outside of the meal. They can easily pick up hot dog/burger/pizza type stuff out by the pool at 4PM or 5PM, go to the show, and then to the kids club while you go to dinner.