I only heard the end of one, and it sounded pretty complicated. The thing is, he composes the score for every instrument in a full orchestra. When he was only 10!
Mozart and Bach have a heavenly simplicity about them even at their most complex.
I'll reserve judgment on the merit of the music til we hear some of it -- that said, it's delightful to hear of a kid being so inspired and working so hard, and his parents supporting him. Hope things work out for him and he has a long and happy life in music.
That's nothing. I once told a dirty joke in front of a classroom of kids when I was only 9! :)