I think that if you are looking in a yacht club they will be harder to find on catamarans - the dingies are just so much more accessible (and manageable) for kids. However, last weekend at Catfest on Lake Norman in N.C., out of 30 or so boats we had 4 that were crewed by kids between 9 and 16 years old (and 3 of them placed podium finishes!). The Seacats in Columbia, SC even have a youth commodore and kids are regularly at our fun and racing events.