Yeah, just be sure to keep an eye on him, and make sure he understands, it is only for outside, when you are around, and not in the closet! I think I would have started him on Bows, first, and then when he is old enough to understand power of fire, and devastation it can cause, and then teach him various methods of fire making. Cute Kid though. Just be careful with him at that age, curiosity, and a new skill can get the best of any of us.
I've been on too many fires, started in the closet, by very young kids playing with lighters, and matches.