It depends on what they are into. Chef Mickey's has all the core characters: Mickey, Minnie, Donald, Goofy, Pluto. It is a buffet though, and I definitely recommend breakfast over dinner there.
For most of the same characters, there is the Cape May breakfast (the food is better here than CM) at the Beach Club. Also a buffet.
There is also the Lilo and Stitch breakfast at 'Ohana. There are, obviously, Lilo and Stitch. You also get Mickey and Pluto. This is served family style, so you don't have to keep getting up, which is very nice. If you make your ADR early (we are usually one of the first tables), the wait is nearly nonexistent. It seems to fill up around 9:30. Those would be my picks.
If you prefer dinner, you can still do Chef Mickey, but we prefer the Cinderella dinner at 1900 Park Fare. Still a buffet, but a better one.
Have a good trip!