My DS will be 4 this trip. He has been about every 10 months since he was 13 months old. We always do buffets and have not yet done a family style meal so my information will only be good for buffet type character meals but here goes:
1) Park Fare 1900 - dinner - As adults we really like the selection here. It has always been great. There is a good kids buffet here and even my picky eater found things he liked. The character interaction has always been excellent here. Characters are the Pooh theme. And, while they aren't my sons favorite characters he still loves to see them...there is just something about seeing them at WDW vs. on TV, etc. Magical ... I guess ... and the adults like them, too.
2) H & V - Lunch - we like the food at this buffet. Is more traditional than Park Fare and my parents really like it. My DS likes the characters - goofy, minnie, pluto, chip and dale. They come around to the tables and really "ham" it up with the kids. They also do a little dance thing in the middle of the restaurant and often have kids participate. This would be a good one at 4 yrs old.
I've read good things about the Princess Breakfast and it is served family style. And, I believe Tony's (moved from Crystal Palace) is also served family style for breakfast. We haven't tried the meal at the Land in Epcot. I hear it is Farmer Mickey and friends. Have heard some nice comments about it also.
Chef Mickey's is not our favorite but many love it. But, again, it is a buffet. The only other one I can think of is Ohana's in the Polynesian. I believe it is served family style. I have read some good things about it, too. Plus, they have activities for the kids during the meals, I believe. Hope this helps.