Bill,
Yes, actually, I would prefer 11 feet or even 10 feet -- the smaller the better (except for the problem with weight-carrying ability) -- because my belief is exactly the opposite of yours. The formative years start MUCH younger. By the time they are 12 or 13, they have other interests and activities, and you have lost them.

Kids need a boat they can singlehand when they are 7 or 8. That is why I have always said they should be started out in the Opti -- besides the fact that it is easier to learn on a monohull, it is very empowering for a young child to be the master of his or her own vessel. So let her take a few lessons on an Opti at the local sailing school, and then put her on the little cat

When they get into pre-teen and teen years is when they want to sail with friends, so it is important that they already be seasoned sailors by the time they get to that point.

P.S.
I was looking again at the pictures of the Arafura Cadet, which is only 11 feet, and that seems like it would work for all the age ranges.