Be very careful of what you buy...a lot of airsoft stuff is pure cheap crap. If your son is starting on a spring powered gun, get him a japanese brand (Tokyo Marui). If he's starting with a gas gun, get him either a KSC or a Tokyo Marui. If he's going all the way for an electric, get him a Tokyo Marui.
As you can see I was way into this stuff a couple years ago before I got my driver's license and my car