I'm 27, so on the older end, but I personally enjoy a mix of EMs, various SS games, and DMDs, anywhere from '62 throgh '99. I wouldn't be opposed to newer pins (i.e. Sterns,) just haven't been willing to spend enough on one game to buy any of the Sterns I would really want.
Back on topic, though - it depends how many games will be there. I'd say go for DMDs or a DMD and alphanumeric (System 11) as the first couple games in the door.
If you're taking him more than 4, then maybe throw an EM in there.