I too, was concerned about this. But only until AFTER I read some threads on the subject.
When we booked, I really wanted the early seating -- but it was unavailable. So, we have the late seating. Now that I have researched this, we are really happy to have the late seating.
In fact, we just returned from WDW and had many wonderful, late dinners with our two boys (7 & 4). We would get them dinner at their dinner time (between 5 & 6) either by the pool or room service and then they would come along with us for dinner (usually an 8:00 PS) and enjoy their dessert. I succombed to letting them play their game-boys at a couple of restaurants (California Grill & Jiko) but I'm over feeling bad about that. We plan to do the same thing on our upcoming cruise.
I want our boys to really enjoy the shows. From what I understand, there is food every where you turn on these cruises, so you certainly won't be at a loss for food.
Have fun!