My friend had a very old dog. That was, blind and deaf. Due to old age.
They kept the dog, in their upstairs floor, which was where the dog was used to. And where their rooms, are. They had a child gate, cordoning off the stairs.
They had, lots of pee pads, lining the floors. The dog was smart, KNEW where everything was, though. It would bark if/when she peed etc.
And the dog, was safe and knew, that floor. So it was okay for the pet. It knew where everything, was. Including her food etc.
You need to think about the safety of the pet, when in this condition.
And leaving things, as is, where it is, so that the pet, can RELY on placement of furniture etc., and get around. They are blind.
And doing whatever else, for the safety of the pet.
When I was a kid, we had a dog that was old and pretty blind too.
But she still got around. But our yard was fenced. And she was safe indoors or out. Our other dog, was actually her... seeing-eye guide dog. Just out of instinct.
For your son, who is nearly 7... he can understand if you explain to him.
Explain fully, that there is safety to keep in mind, for the pet. FOR the pet. He can help, when/if the cat is not safe or about to be in an unsafe predicament. My son is 7. We have a pet bird that is very ill and fragile and weak now, don't even know if he will live. My son, watches out for him even if he is a caged bird. He handles him, VERY tenderly. VERY carefully. And if the bird is stuck, in a corner of the cage etc., he will help the bird and tell me. He knows the bird can be in danger at any time, due to his fragile condition.
And he is very gentle and aware with the bird. I can trust him, with doing it.
Tell your son, explain to your son, that the cat is blind. And needs looking out for. He is old enough.
He can do it.
Show him how. And to handle the pet very gingerly. Because, also, when a pet is blind and their senses are limited, they can get more defensive. Just out of self-protection and instinct. They are very, vulnerable in that state.
Also, since the cat is blind and not able to gauge heights as well etc. it is a danger for him to get down or up, to things of height.
So keep that in mind. Even if he is a cat, and that cats a supposed to be able to land well on all fours.
So yes, get any step ladders/stools etc., to help him get up and down things. As necessary.
I would ALSO, if you do not already have it, put a cat BELL on him. SO that, you all will know where he is. And locate him.