They can still be innocent at nude beaches. There aren’t any orgies there or whatever you think a nude beach is.
Creeps gonna creep. Only way to avoid them is to not go outside. And honestly who cares? Maybe I’m a bit desensitised, but if someone stares at me at the beach, why should I care? Same goes for the ones staring at children, with the difference that children don’t even worry about stuff like that. I also think you overestimate the amount of people who actually go there to creep. It’s not even necessary to go to a nude beach for that, I’ve seen plenty of naked kids at regular beaches.
“[…] because they don’t understand the severity of the situation.” What severity? What’s going to happen to the kids? Do you seriously think they worry about being sexualised? When I was a kid, we would run around naked in our backyard, lots of neighbours were able to see us. Did I worry about that in the slightest? Nope.