Get an adjustable youth sized release. Adult releases are not for kids, trying to learn how to shoot a bow. Like Shaw said, he'll be trying to reach out to get the trigger. I'd start him on the release because for my 2, it was easier for them to repeatedly shoot accurately with the release (they like hitting what they are aiming at or at least close to it) than it was with fingers. Get back on here in a couple years and remind me when he gets to be 8 or 9. I should have a couple good youth bows freed up by then that he could have to chose from. One is a bowtech and the other is a PSE. Fully adjustable DL and poundage. My two boys shot them from 8 til about 12 or 13 and both killed their first bow deer with them. My nephews are currently using them now or I'd offer them up today.

Make it fun for him and expect to loose a few arrows along the way. LOL