Make a good name/impression for yourself first (which shouldn't be a problem by how you've already conducted yourself on the forum so far, much better than some self described "mature" minors or even some self entitled "adults" (18+)), then bring your son out to spectate and then ask about bringing him to play.
Keep in mind, baby steps. You can't expect to just show up as a "random" and bring your son out to play but once people get to know you they'll be more receptive.
One more thing; some fields are 18+ only, period. Others may be 18+ or have parent/legal guardian in good standing to allow younger. Some may be 16+ and parent must be on field/spectators area at all times (this is to prevent mommy and daddy dropping the kid off with money and taking off to do whatever like it's some daycare).
Just ask, it doesn't hurt.
As for gear, rent first and see if you like it. If you come from a paintball background it's similar but different. Some games are run like speedball but you'll mostly be playing woodsball style, some quick objectives, some longer objectives, and the occasional long daysim/multiday sim (if you sign up for one and think it's something you'd like).
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE