Hi Stephanie,
I presume he hasn't played a game at a site yet?
If that's the case then he doesn't need to join a team to play. Many of us (including me) started just by going on our own and meeting people during the day.
It may be a bit intimidating at first but most are helpful to new players.
I took my son when he was 14 and its a good bonding activity for father and son.
When actually playing, everyone runs in their own direction so he can just follow along with anyone.
The main thing is to obey the rules while having fun. When shot, raise hand and shout 'HIT' so that he doesn't get shot anymore. With hand raised to show he's out its just a case of walking to an area to respawn and join in again.
The most important elements are good quality eye protection (not mesh) and boots with ankle support (army surplus is good for this)
Good eye pro would include:
Bolle Tracker
Bolle Pilot II
And face protection like
THIS
If you need to find a site near you then have a look
HERE
It may be a bit out of date so some of the info could be wrong but its a place to start.
Alternatively search 'airsoft' in Google Maps around where you live.