My son turned 7 back in May. He killed his first turkey in April with my 1187 20ga. It has a vortex venom on it, and shot with TSS handloads.
We cheated, we were in a blind and had the gun in a death grip tripod. All I did was call and he done the rest. After that I bought him a mossberg SA28. It is compact with a lot shorter lop. Very light and shorter barrel. He loves shooting it but is very loud due to the barrel length. I make him wear hearing protection anyways, I figured this out when I was shooting it. It will be a while before I think he will be ready to hunt in the open or without some kind of good cover bc he can’t be still…
Good luck with your search