I'm sure you probably already have this set up, but a carnival would be fun. You could incorporate activities for the different age groups. A band (live music) or one of those bmx stunt teams could perform. I don't know where you are located so can't really advise on music but I do know of a bmx stunt team called perfection on wheels that travels the west and east coasts. There are also tons of sites that give carnival game ideas. Good luck! J
What kind of celebration are you thinking about -- family day on weekend, during school, community project? Any beginning ideas that maybe other leaders can add to?