For dinner, you are assigned a "rotation". We last sailed on the Magic and I can't remember the names on the Wonder but lets call the restaurants A B and C. If your rotation is ABCAyou get A the first night, you'll get B the second, C the third and A again the 4th. If your rotation is BCAB - you get the picture. There have been postings at length on which is the best rotation with kids - we liked all the restaurants. One of the restaurants is a bit more formal so if your kids don't do well - sitting still and all - you might not want to hit that one twice.
Early and late dinner times have changed up and back - first seating is in the 5:30 - 6:00 time frame, second seating is 7:30 - 8:00 or so. Whatever the times are, you want to be ON TIME as they do not serve the table until everyone is seated so you are keeping someone else from eating. Our first cruise we did the early seating. For younger kids it might be better because they may get hungry earlier, tired earlier, etc. But, it can also really PUSH you if you do an excursion and don't get back until 5:00. For our second cruise, we did the later seating and liked it a lot better. After dinner our kids (teens now) were ready to hit Common Grounds and we usually went to one of the clubs. If we wanted to see a show, we saw it before the later seating.
For breakfast and lunch, I think you can do a formal sit-down, served thing if you want to but we just went to the buffet in the top deck restaurant. The exception is the last morning - you have a sit down breakfast in the same restaurant you ate in the previous night. I guess they want to control things to get you off the ship. There's also pizza and hamburgers available around the pool.
Don't stress over the details - I'm glad I did not discover these boards until after our second cruise because I'm a PLANNER. I would have driven myself nuts and not had any fun if I knew there were so many things to stress out about. Disney does it pretty well without us going nuts!