I started on and 870 and still have it, 30 years, and love it. It didn't fit the best when I was first starting. I think your issue was recoil. Sounds like you need a gas gun. Lots of good ones but I kind of like the 390 or maybe it's a 3901 youth. Has a gray stock with a section you can take off to make it shorter and then put back as they get bigger. Won't last them forever for fit but should go a good long time. The berettas also have a stock shim system that allows for fitting the gun to the shooter. Hard to go wrong with that. Just got one for myfriends son. He loves it and has no complaint about the recoil. I think it is lighter than the remington auto. I am sure there are other good youth models out there, this is the only auto other than the remigntons that I have had alot of first hand experience with.
More ammo! I need to shoot something!