Don't wait. If you do they will find the opposite sex and piercings and won't want anything to do with your camping! Get them doing it while they're young, the risks are minimal with two parents looking after them. Teach them what you know, get them involved in putting up the camp, even if it's just collecting wood for the fire, whatever they want to do to help out. And while they are learning that you can sneak in your safety rules.
Just don't assume they know not to go chasing lizards under logs and rocks... I didn't know not to do that when I was ten! lol I chased a blue tongue under three or four sheets of roofing iron before I caught him on my brothers farm one hot summer day. Never occurred to me reaching under a hot piece of tin was a bad idea. City kids, what do you do with them? lol
So just give them a few safety rules and since camping is new to them they'll find plenty of safe fun out there. They can just as easily fall in a hole down the local park as they can out camping.