I had to wait until I was 12 and had my hunters safety class finished. I then had to hunt next to my father for two years before I was allowed to hunt in the family hunting camp up by Superior,WI. But as I was growing up my father would take me on squirrel hunting trips with my plastic toy assault rifle. He taught me many lessons on those trips
I have taken a similar approach with my step son and will do the same with my son. My step son is now 11 years old. When he turned 8 he was allowed to come to our camp and hunt with me in a blind opening weekend only. Not my preferred stand for gun season on our land but I am more than willing to sacrifice opening weekend hunts for time with my little buddy.
At 9 I allowed him to carry my .22 rifle with no ammo to teach him gun safety and muzzle awareness. That same year my neice came along so I also took her on a few hunts repeating what I did with my step son. That season I harvested a Doe that we had targeted for being mature and dried up.( no fawns for 2 years) I had them both present for field dressing the animal. My father dressed my first kill (at age 13)but I had to watch so I knew what to do. After that he would guide me as I dressed the animal until he knew I was going to be ok. In our camp we rarely do it alone. Someone is always willing to sacrifice time in the woods to help a fellow hunter. They both got through my field dressing better than I expected for their first time.
At age 10 my step son hunted with his dad opening weekend. And my neice sat with my brother and he shot a buck and she did better with questions and remembering what to do.
I am not saying the way we do things is right or wrong. But it works for us in nurturing new hunters into the fold. When you spend that amount of time with the kids in the woods, you will know who is ready and who is not.
As far as the responsibility of the kill and taking care of the animal. That falls on the mentor. To teach them the morals and ethics of hunting and conservation. They are the future of hunting. Take them, teach them, and know your lessons will forever be alive in their minds and when they teach others.
I have taken friends hunting , that I would shake my head at the things they were never taught. Its just like anything you will ever do in life. You will get out of it what you put into it.