Pedophiles can be ID'd from parents' photos. If a child disappears from the rink, maybe a parent running video or taking photos will catch the guy in a shot and help the Police to identify him.
Banning photography of kids will not stop a pedophile. They are probably doing it anyway, using cameras hidden in their clothes (like the ones on shoes to get photos up women's skirts). Besides, the pedophile doesn't need a photo to get their jollies - they're there anyway. just watching.