Call and email EVERYBODY, and let them all know who else was notified.
This way, from the get-go, all parties know that everything is “on the record” and no coverup is possible.
This article gives instruction of what you should do from the point of view of a parent. Police should make first contact with the perp and his organization about the charges.
Before they move in, you really don’t want the perp and organization having the chance to figure out their strategy to avoid the responsibility, destroying evidence and lying about it. Shock is good.
Also, in court the perp will find out which victim called the cops and by then he had best not contact and harass the victim. The same with the organization that hosted or employed him. That would be tampering with a witness.
Also, the boy will have a chance to file civil suits the organization and perp and you don’t want to give them a heads up on what your case will be. They are all legal adversaries trying to protect themselves against your boy.
The state’s children’s protection agency should notify the children’s organizations he has access to, that the perp has been arrested for child molestation. I know a family who had to move out of the State because the perp was dangerous and made bail. It’s nasty stuff.