If an airsoft gun is a paintball gun, then yes. But there would be some rules.
1. The gun is ONLY used on the paintball range/course/field whatever and I keep it the rest of the time. Those pellets can break windows and put out eyes, especially in the winter when they get frozen.
2. Protective goggles WILL be worn at all times when using the gun.
3.
If you lose a testicle (happened to a friend of mine), I WILL say, "I told you so." Because I've never met a man or boy yet who's willing to wear a cup, and really, they all should.
4. And no b*tching if I decide to rent me a gun and to come out for a game or two myself.
Paintball is outrageously fun! Not totally safe, but definitely fun. I think it's fine for 12yo boys, but your son may be a bit shocked at just how much getting shot with a paint pellet hurts. Oh, and he'll have little round bruises, too! You can have fun counting them the day after.