I'm throwing a birthday party for my friend who's retarded..need help?

My friend James is a retard (technically not being funny) and me and my friends are going to throw a party for it Saturday. We wanted it to have a retarded theme so it would feel more comfortable and have fun. We couldn't think of exaclty HOW we could make do this. What kind of decorations should we get? What kind of food should we feed it? We were thinking little paper dumbbells or books with question marks above them, but all of it just sounds rude which we don't want to be. Any suggestions of what may work?