Jake, my 8 year old deer hunted for the 1st time last season.
I'm not saying it's the best, but I bought him a .243 youth model bolt action.
Little did I know (until a friend of mine educated me) they can load 'reduced recoil' loads (for any caliber I'm sure). We started light and worked our way up prior to hunting. The 1st time he shot it we started on a lead-sled, then a shoulder pad, then nothing but the gun. All in the same day. The reduced recoil was the key. Being he was only 8, recoil was an issue.
I think making sure the young one isn't 'scared' to shoot it is important.
Jake connected on the 1st day of his first hunt. Thanks to a friend that was our guide. Still my best day hunting ever.
-John