Agree w/ the palliative care. I currently have a cat that cannot walk at all. She's otherwise happy, eating, purring, etc. I carry her to the litterbox several times a day, bring her food to her, give her water w/ a syringe (she won't drink enough otherwise), take her outside and sit w/ her a couple of times a day. When I pick her up she leans her head on my chest and the purr machine goes into overdrive.
She has neurological issues and could get around very, very slowly until a week ago, when they steroids seem to stop working. She's happy, and in no pain. Her vet has never pushed to have her put down. If she were in pain, or when she stops eating or is in any kind of distress, we might rethink things. But right now, she's happy. And very spoiled!