Well, when my daughters were 6 & 8 years old, they decided they wanted to go deer hunting with me. I had access to some private property with a lot of deer. So I wired three palets together, put burlap around them & them zip tied bushes around all of that. I put chairs on the inside & we would sit there & watch the deer as they would walk across a long road (each had binoculars, I had a scope). Well, to make a long story short, they had to try to shoot one themselves. Nix'd that telling them they had to practice shooting & consitantly hit the bullseye before I would even consider letting them shoot at a living animal.
I bought them a 357 Magnum, single shot rifle (breach action & have to cock the hammer). Let me tell you, those girls were naturals at it. They spent that next summer practicing & eack bagged deer the next winter (have great vidios of multiple hunts) & continue to bag them every year. They are 17 & 19 now (boy how time flies). They are the greatest kids a dad could ask for.
Moral of the story: It's all about teaching responsable, safe use of firearms and knowing when your children are ready. And they are all different. Idots with guns come in all ages.