When we went to WDW 3 years ago, we did 3 character meals. The best character interaction we had was at Garden Grill. This restaurant didn't feel at all crowded and when the characters came around to our table, they really spent a great deal of time with us - not only doing the required autograph/photo pose. At one point, Pluto had DS on the floor in a tickling contest! The rotating views also adds some interest when the characters are not there. The food was very good - not our favorite, but good.
The second best character interaction we had was at Crystal Palace. All characters came around and a few spent more time playing. Tigger and Pooh grabbed DD's stuffed Eeyore and played catch with him for a bit. They didn't spend quite as much time with us as at Garden Grill, but it was still great. The food here (dinner) was our favorite.
Our last character meal was the Cinderella breakfast. The characters were good, but didn't seem to do much more than make the rounds to sign autograph books and take pictures. Maybe because they are "princesses", they didn't seem as spontaneous and fun.
This is just one experience and was 3 years ago, so take it for what it's worth. Have fun planning and enjoy your trip!