I'd go with Boma or maybe Jiko. If you get an early res, you can do the culinary tour (sometimes at 3:45, sometimes at 4.) I went to dinner at Boma, and went back a few days later to do the tour. I wished I were eating at Boma all over again! The tour of Boma happens just as they are setting the food out for the evening meal. There is plenty of grown up fare--not your typical buffet. And if the kids are not adventurous, there are plenty of kid picks available as well.
The MK is an easy bus ride away.