My daughter has Tay Sachs Disease, what are some good activities I could do with her?

My daughter has a form of Tay Sachs disease (a genetic disease), she has progressively been getting worse. She experiences a lot of involuntary movements and is unable to walk properly and can't control her bodily functions at all, She's lost a lot of weight and awareness. She is unhappy sometimes but I'm not sure what I can do to cheer her up. I was just wondering if anyone had some suggestions on some kinds of activities and things I could do that might help her (mentally and physically)? I know I'm not going to cure her but I have to help her the best I can. I've been taking her to the swimming pool for a type of physical therapy. My other daughter is two, she doesn't have Tay Sachs and doesn't understand her sister's disease yet, and I'm trying to think of other activities I could involve her in too (with both of them).