In the Neuro ICU where I work, we almost NEVER let a child of that age into the unit. First of all, a child of that age is not psychologically capable of handling that. Secondly, (not to be rude about it) children carry all kind of nasty bugs and viruses!
I have only seen it happen one time, and in that case, not only did I get the social worker involved, but also I had a Pediatric Nurse Practioner come down.
In my unit, I try to not only protect my patient, but the family too!