This is something I really agree with. I feel like encouraging people to actually cancel their reservations so that other can use it would be a big help.

I see it working this way: keep the fees for camp sites reasonable, and you get most of it back for cancelling 2 weeks out. As you get closer, a prorated added cost to cancel. Fail to cancel but don't show? 25% no-show fee applied straight to the card on file, automatically. Watch the behavior change overnight.