Oh dear be
I've worked with enough handicapped folks to know that no matter how severe the illness is, they still have senses and know when things are "off" or "not the same". It can bring about some real anxiety and their stress levels can go sky high

As for the 9 year old....since my grandson is the same age, I can well imagine what he's thinking.
One thing my aunt told my grandson the other day..and I think it helps him is this - "Your daddy didn't leave you, he left the world. But he will always remain in your heart and your mind." Maybe that would help?
xoxoxo
sabby