Re: How to introduce shooting and hunting to children...
My oldest is 4, and he has intetest as well but is a little intimidated and his attention span is short. We started him on a pellet gun (supervised, of course) last summer. It was a good tool to teach safety, aiming, etc. He enjoyed it, but only for about 10 minutes at a time. I didn't feel like he really loved it, and I never pushed it - if he asked we would go out.
Over the winter I bought him a cheap Rossi single shot 22LR, and went out with him a few weeks later to get targets, hearing protection, etc. The other day was nice and he asked me to shoot. The mix of the new equipment, the build up, and the "real" gun did it - he had a ball. After about 20 minutes his attention started to wane, so we wrapped up. But he's talked about it every day since!
My advice is to start small and slow, and don't make a production out of it. If you can find a non-range environment I think that is best. 22LR is a great start - quiet, cheap, and readily available. Well, it will be again someday! Emphasize safety and make it fun.
Good luck with a great father/son activity. If he takes to it some squirrels may be in order!