My kids were 4 and 6 when we butchered our first. I was even younger myself back in my day, we always had chickens for meat as well as for eggs. Kids can learn and get used to anythingHaha. The attached kid is the hard part. Telling her one can't stay. How does it work out keeping 2? They're already at it so probably not good.

Keeping 2 roosters who want to kill each other isn’t any better for a kid. There could be blood, raw injuries, slow death. Might as well go with the circle of life lesson and a nice meal or two instead.
I would not keep any roosters with kids around though. Kids and roosters don’t mix well. Success stories are rare and not worth the risk.