How about walking the dogs at his local animal shelter? Would give him doggie time and exercise!
I wouldn't let him pish pish volunteering with different ages, after all, senior citizens have granddaughters

. Volunteering to help coach a middle school or even elementary team would give him the knowledge and network to move up.
He must have many local, state, and maybe even national parks nearby, he could start a log and even blog. One sticker will usually get you in for the whole year, and they are wonderful to explore (and more exercise).
A part time job might seem like a bit much, but he's at a prime age for socking away savings and letting it grow, especially since he doesn't have the responsibility of a wife and family yet.
I feel for him, I know a LOT of young men in his situation (since I work at a technical college). If they don't hang out at bars, or have a girlfriend/wife/family, it can be pretty slim pickings in a small town.
Terri