I have four kids. I taught all of them to sail on Hobie 16's. This year the two oldest will race against the "old man" in our club races. Should be a blast...no pressure though!...HA
I have found when you teach a kid to sail you have to be smart about when, where, and under what conditions you go out in. You don't want to start when it is blowing the lids off the trash cans. It may be fun for you and I but not so for a kid.
You also need to know when to say when. As soon as it is not fun for them (could be 10 min) you need to get off the water. I have found that if you press the issue by staying out longer you are less likely to get them on board the next time.
Let them sail the boat while you crew. They will have the thrill of "driving". Of course do so in an environment that allows for a mistake.

have fun!

John