Don't know about 6 or 7 year olds but my rather particular then 11 yr old DS loved Boma during our last visit to the World. I will qualify by saying not sure he really ate much of the African fair. The buffet does include several soups, though, and one of the at least 4-5 offerings (they switch them out, depending on the rotation, I believe) caught his interest that night. He mentioned the french fries were good, the ground chick pea balls (I can't remember the real name for them), and he also really liked the selection of desserts. Maybe not the most nutritious choices, but hey, it was just one night on vacation.
So it was a winner for him, while I was a little disappointed with Boma, and I had really been looking forward to it as had cancelled reservations the visit before and had heard such good commentary here on the boards about it. For me, I really didn't like the sweet element to a lot of the options. I certainly found enough to eat, though; the soups were tasty and the curry pasta salad was a standout for me.