You're probably worrying about nothing. If the campground you're in is not safe enough to leave them, I'd pack everything up and get out of there in a hurry - its not safe for you either. At least in the areas we frequent(Colorado and New Mexico), campground safety has never been a concern, but I don't know how MO is. We've found that people who go to campgrounds are generally very friendly and would be glad to help your girls if they needed anything. Have you met the people camping nearby? Do they seem trustworthy? If so, would they keep an eye on the girls? No doubt the girls are able to take care of themselves. My friend and I started backpacking (just the 2 of us)in Colorado when we were 14. Nothing more than 3 nights, but we had a ball! Let the girls develop their independence as much as possible!