There's a good reason to keep animals and birds away from playground sand, and it's zoonotic pathogens and/or parasites that can cause serious harm, resulting in illness, blindness or other nasty infection. Ringworm is something relatively benign when compared to other possibilities. 

Here's the problem for an outdoor playground, is it even possible to prevent birds and animals from accessing playground sand when outdoors? Can it be properly cleaned and disinfect it? 

The short answers are, "No," and, "No way." Daily raking to remove some animal waste is not even close to getting all of it, because it is merely distributing the pathogens throughout all the playground sand. There's really no effective or efficient manner to clean and disinfect a 12" depth of playground sand. 

This is exactly why the NRC recommends either using playground sand only in indoor playgrounds, outdoors only when under constant adult supervision, covering it when not in use, and removing and replacing it every two years. Essentially, it's a giant litter box, except feral animals use it, too. 

In one playground, a nearby infrared night cam captured a mountain lion using the sand at least 3x a week, sending a message to the local pets about who's territory it was.