It's none of the other parents business who is and is not immunized because as long as THEIR child is immunized they should not have to worry. And really that is personal information that I don't think you should be sharing. However you should have the parents of the non vacc. child sign some sort of waiver that you will not be held liable should this child become sick. And also if there were to be some sort of measles or other outbreak the parents have to agree to exclude the child from care until the threat is gone. There is a waiver of some sort that parents have to sign to enroll their child in school, maybe you could try to find that and sorta copy what is says and get the parents to sign it.