There is plenty of food available on Deck 9. When we had late seating, the kids ate pizza or burgers around 4:00 on deck 9. Then we would go to the show together and eat at the late dining. We had late dining on 4 cruises, and we found that when we were on the Magic and wanted to do excursions, that late seating worked good. When we got back to the ship from our excursion we would order room service while the kids bathed and we got ready for the show. When we went on the Magic once with the early dining we felt VERY rushed to be back on the ship and ready for early dining.
So if we are on the Wonder, I prefer early dining, but on the Magic we like the late seating better (because we do excursions on the 7 night, but on the 3 and 4 we don't bother).
Don't worry, no one will go hungry, and the kids may enjoy the show better in the early part of the evening, and for them that is one of the highlights of the trip!
DJ