It is ok for you to be cautious. The parents of the child should also be cautious. I am no doctor but I thought people with HIV or AIDS should be careful about picking up things from OTHER people. I would not want the tyke potentially swallowing pool water, etc. An infection or bug that a so-called normal person can handle can endanger someone with compromised immunity. I think.
My heart goes out to kids and people that gets this stuff....Jesus hung out with the lepers, I probably couldn't. But after all, that's why HE was Jesus and well, I'm an uncivilized superstitious barbarian. :-)