Are you right in DC, or in one of the suburbs? There is a cooking school with kids cooking classes at Dulles Town Center. Probably wouldn't be too convenient if you're in Maryland or DC, but if you're out this way it may work for you...
I was actually at that mall the other day for something else, and was able to see inside as I walked past--the kids in there (older--maybe ages 10 +?) looked like they were having a good time.
http://cookologyonline.com/