Blackrain, great post!
I agree with eveything! Gun safety is the most important thing! I always say, "the best safety is your finger!" Keep that finger off the trigger until you're ready to fire the gun. Once the trigger is pulled, you can't get the ball back, so be sure of your target!
I played on Saturday and we had several newbie kids and some Dads out there. I had to tell one boy four times to keep his mask down!
Paintball welts heal, but you can't regrow an eyeball!
You're also dead on about the "flashy outfits" look for the older guys wearing faded camo, odds are they've been around a while...
Also, like you said RENT First! Yes, rentals usually suck, but it's better than making a major investment and finding out that your offspring has changed their mind about the whole thing.
Be wary of used markers at some dealers, if it sounds too good to be true it is! My neighbor didn't listen to my advice about buying a Tippmann for his 12yr old to use in the woods and was "sold" a used Ion which never has worked right!