Take them out in conditions that are windy but not crazy. Buy and teach them how to trapeeze, they will learn very quickly. PFD, PFD, PFD.

TAke them out in light wind and tip the boat over, let them jump off the top hull, just have fun swimming around the boat.

I reccomend racing in a low key manner, with getting them involved in timing the start and spotting boats and marks.

I now sail/race almost exclusively with my daughter (13 y.o.) in all levels of competition. She loves it and has made many friends from around the sailing world. She can't wait to go to the next regatta. She raced her first National's (barefoot, no less) with Mike Siau (17 y.o. at the time) in 06 at 10 yrs old. HUGE WIND and WAVES!!! Never really worried about them, even after flipping multiple times.

Pics are her and her mom racing in a little wind (15+) when she was 11.