The LAST gun in the world to start a new shooter with, old or young, is an autoloader. Yes, you can load one round, but, that bolt going back and locking open heightens the sensation of recoil.
I'll stand by that. Nine years of age is a bit young for a first shotgun, in my opinion. Recoil and blast imact little ears and frames at that age.
At nine, my kids are all still enamoured of the lowly .22 rifle. That's enough, at that point.
Best,
Ted