Kids love Sports Champions.

Heard Killzone 3 was good for move.

i think move heros is mutiplayer

As someone who has had a Move since launch and has purchased tons of Move compatible games, I have to say, there are many games you can choose from.

I'd highly recommend Start the party. Really awesome game for any age really (btw you only need one controller for this game).
Sports champions is really fun and I've read that its sequel is just as good.

I'd recommend more, but there's no point. Just get them Start the party or its sequel (whichever is cheaper)

Oh, and here's an awesome site about anything move related http://www.pushsquare.com/news/tags/Move

There's the wonderbook bundle. Plus I'm assuming it'll get more support so it won't be just a Harry Potter simulator.