Don't let that get in your way, check first to see if your parents can make reservations for you, and if someone has to be 18 with you, either just stealth camp somewhere, or just go to the campground anyways. Back when I was 16-17 we camped at places all the time, just showed up right before dark, and if they asked for ID, just say you don't have it on you. In 90% of cases they will let you stay there anyways.