I know a guy who years ago hunted deer with a 410 because he thought it should shoot like a rifle at long distance. Lucky every time he went he didn't see any deer and stopped deer hunting. He wouldn't listen to me about the 410 and long distance.
If you do not have a viable gun for him to use I will let him use a 20 gauge of mine I put together for my Daughter-in-law last year.
It is a H&R single shot, Ultra Slugster, with a red dot. It should be a pretty easy gun for him to shoot and it eliminates the killing capability concerns of his gun.