This is so my 9 yo son as well. For a while this year it was Rube Goldberg machines. Then magic. Last year it was greek mythology. First grade pokemon. On and on and on!

We've chosen music as our "stick with it" thing and it has worked very well for both our kids. They both enjoy it most days. And my 9 yo has enough mastery now that I highly doubt he would want to quit. We'll see how it goes for the teen years!