Linda,
with my girls a buffet is a great play, since I can get them whatever they want to eat, and more importantly, a little of a lot of the things that they want.
But which are the best, food wise? I would go with these;
Boma: I love the opportunity to visit the beautiful Animal Kingdom Lodge, as well as for the food. What I enjoy is that they have many American classics and some African and Indian inspired options as well.
Tusker House: This is a copy of Boma in many ways, but I mean that as a compliment. At dinner there are no characters, which for many is a plus.
I would also consider
Biergarten in Epcot. While they are missing a few of the German classics, I think they do a fair representation of German cuisine. The band, as well as the more familiar and social nature of the restaurant is quite enjoyable.
But what about all the famous character greeting choices, like Chef Mickey's, Crystal Palace, and 1900 Park Fare? I think they all have food that is just OK. In all three cases you are going for the entertainment more than the food, but they have improved the food. Of these three, I actually prefer 1900 Park Fare, but in all cases you should choose based on where you are, and what characters you want to meet, rather than on the food.
I love the dining questions!
Have a magical (and delicious) vacation!