I have to agree with just about everything said, but most importantly safty first, get him through a certified safe hunter coarse.
Get him shootin a .22 and a .410gu, single shots by all means if he starts too big and gets booted by too much gun all could be spoild.
I wouldn't recomend Turkey huntin with a .410, although I'm sure its been done.
Now that he's been introduced to shooting and a lil recoil, let him know he's guna need a bit more gun for serious huntin. Try to let it be his desision to move up to a 20gu.
Not that long ago single shots 20gu on up were primarily only available in a modified choke. I don't know of any other brand but a Rusian company called Baikel is making some pretty fair single shots with interchangeable choke tubes. A real nesessity.
This is a pic of my 14 year old daughter with hers 20gu. The gun has a vent rib barrel and interchangeable choke tubes, I added the sling and scope. It paterns exalent with the full choke tube and hevishot out to 35 yrds. Come Fall install the improved cylinder choke and it shoots slugs like a dream, around $150. Recoil is no heavier than my wifes Mossberg pump.
Single shots develop shooters, A teacher at school was asking Melony all about getting this Deer. A boy in class asked her ''why didn't you use a pump or semi-auto, you would get a second or therd chance''. The teacher asked Mel ''how many shots did it take'' Mel modestly replied ''just one''
''Develope a shooter not a flincher''

http://img.photobucket.com/albums/v3...owrio/3249.jpg