LINCARE what may be more difficult, even possibly impossible is ensuring that his nieces and nephews can inherit. I am thinking that he might need care in his turn and unless he has a dependent living in the house, then the house could be included in his financial assessment.
I am not sure if this is right but possibly putting the house in trust for your grandchildren with a lifetime interest in your son might do it but I am not a legal beagle and you will need proper advice.