Karen,
Easy questions! The best princess character experience, in my opinion, is
Restaurant Akershus in Epcot. Most seem to prefer
Cinderella's Royal Table at the Magic Kingdom, but I prefer this one for the variety of princess characters that attend.
For a 6-year old boy, I like the Mickey Mouse family of friends at either
Chef Mickey's (Contemporary Resort) or
Donald's Safari Breakfast (Animal Kingdom). I think the latter might actually be better, as the safari setting makes it even a bit more fun for a boy!
As for a show, I think that the best one for both is to go to
Mickey's Backyard BBQ. It is great fun, has good music, great food, and a unique experience for the whole family!
Please feel free to send along any follow-up questions!
Have a magical (and delicious) vacation!