One of my policies is
I hold the right to ask for a Doctor's Note before your child can return to care.
I also have the right to refuse a Doctor's Note, if I feel that your child is not ready to join in all activates or just isn't ready to return to care.
This covers me if I feel that the Dr. was just being nice and helping out the parents with the note, I know too many people who's Dr.s don't care and will just write a note saying whatever, even if the person wasn't sick or should not be in daycare/work etc. I feel that most Dr.s notes these days are jokes, but it is always good to ask for one anyways. If something happens and a other child gets the virus/rash or whatever and the parents go after you for it, then at least you have a note stating the the child's Dr allowed the child in care.