RE: first board for kids
My children are 9 and 11, and the heaviest weighs 90 lbs. I purchased the Starsurfer S for them and they really enjoy it. Granted it is more tippy than a big stable Go, but with a small sail and light breeze they were moving in ten minutes. It is very easy for them to tack. I use a rope attached to the center fin so I can drag them back when they get in trouble.
Here is the best part. I tried it this weekend in 25 knot winds with a 5.6 Hucker. I have never used a board that could rip a jibe like this one. Wholly crap! ALso, due to its lack of a nose (i believe), the thing just stuck to the water. I figured it would fly away in the really big gusts....not a chance.
Get a board that has better performance "for your kids" vs a big wide door type board. "They" will really appreciate it.