There are a lot of very inexpensive electric “Almost Ready to Fly” RC planes available at Toys R Us, Target, etc.  I’d start with one of these just because they are cheap and tough.  It takes awhile to think 3D from the perspective of a little plane that you are looking at from various angles, and to look ahead, react to gusts, etc.  Especially when you’re a little kid without much experience to draw from.  Let him get used to a couple of these little $30 planes and then get him a real RC trainer.