I killed my first 6 deer (the first when I was 9), nearly every rabbit I ever killed, and a few turkeys with an 870 Express Youth Model 20 gauge. It's light enough I can hold it out with one hand and shoot it with small shot. My dad's actually got caught with his pants down and done that. Funny story. Killed the rabbit too. A .22 would make a better first gun, but it's definitely not a deer gun, and questionable as a turkey gun for somebody inexperienced if it's even legal where he lives. My 870 will drop a deer at 50 yards with #3 Buckshot, and will blow a squirrel out of just about any tree around here with #4 fine shot.

That being said you know your kid better than anybody here. My dad started me with a single shot Stevens 20 gauge and stayed real close, cause he felt it was better not having the extra stuff to worry about (pumping, push button safety, etc...) that the pump has on it when I was learning. After my first year with the single shot squirrel, and deer hunting (never got a shot at a deer) my dad felt I was ready for the pump, and that's what every shotgun I have had since has been. I've never had a problem with recoil, and personally would not want to have to deal with the extra problems associated withsemi's such as not cycling if not held exactly right, and jamming while also trying to teach somebody new to shooting how to shoot.