Garden Grill in Epcot - yes, it's a character meal too, but it's also all-you-can-eat, straightforward cuisine, served family style (= no trips to the buffet, instead they bring it all to you) with things to look at which shift/change during the meal. Also, the seating is in booths which make the overall experience quite personal - most of the time, the only people you'll be able to see are your own family, the characters, and your server. (Can help keep little ones from getting overstimulated, we've found.)
Ohana is another family-style that is good for small kids if they enjoy watching/listening to activity around them. The atmosphere here is much noisier and more frenetic than at other places, which is a plus if your kids are people-watchers but maybe not so much if activity/noise puts them on edge. If your older child is outgoing, there are games and activities too (your younger one will be a little young to participate in most of it).
