I'd like to thank Chris for his great response regarding kids playing music. I admired his technique & his ability especially with the classical guitar.

After reading ajustinbryant's post my first thought went to Sinichi Suzuki who began teaching children as early as 3 years old. They have the ability to learn quickly, just as they do learning a foreign language at an early age. They haven't learned the bad habits yet.

Just find what holds his interest. My opinion would be to take him to a full range music store like Sam Ash where he can see everything. You never know, he may end up playing clarinet & bringing Benny Goodman style swing back in style.