I concur completely with Teak. It is NOT your job to inform anyone about anyone else's medical history, including HIV. This is why the HIPPAA laws came into effect, to protect people's confidential medical records and information.
HIV is only transmitted vis unprotected vaginal/anal intercourse, sharing IV drug works, and via mother to infant. There is no risk through casual contact, or from environmental surfaces.
This is info you need to keep to yourself, and if your co-workers are blabbing info to other people they learned on the job, you had better inform them of the risk they are taking.
Matter of fact it's against the law for you to inform anyone of anyones medical details which includes HIV status. Doing so, leaves you at risk for a law suit. Read the HIPAA laws.
there is no reason for you to tell the parents...you cannot contract hiv through casual contact.