Watching
My mom is blind as a bat without her glasses and when I was young she would tell me she was going to shower. I would wait for her to get going then sneak in and sit on the floor and watch her shower through the glass. I had done this for a few years mostly during summer vacation, one morning I was laying in bed and I heard the shower turn on so I jumped out of bed and crept into their bedroom. I got into the bathroom and there she was in the shower as usual. The shower had a removable shower head so she could hold it and move it all over her body. After she had washed her hair and body she put her foot up on the wall in the corner, turned the shower head to massage position and put it between her legs. Her other hand was on her breasts pulling on her nipples and she would also use it to spread herself out for the water. She was moaning out and after about five minutes her legs were moving around and she had an orgasm. Over the years I only got to see her a masturbate with the shower massager 3-4 times but it was great each time.
Do it if you can. I watched my hot older sister from a crack in the door, take her shower, soap up her amazing body and mid back-length hair, finish up, dry off in front of the mirror, including powdering the bottom of her tits, all the time. When she'd come home from a night out and needed to douche out, she'd lay on the bathroom floor, legs spread wide, and, even though her face was directly in view, there was a great blind spot from the floor that prevented her from seeing me watching her. She'd move the plunger in and out of her hole to douche out, towel underneath her, and making faces of pleasure as she did it. Her knees would be in the air and I'd see both the plunger thing and her long, red-nailed fingers up inside of her, giving her more pleasure.
She eventually found out about the shower watching, but didn't care, and started to leave the bathroom door open so I could just go in and watch and talk to her directly, but didn't know about the douching-out show she put on for me several times. We had a great, long talk about our past on the way home from a road trip one weekend, very up front about her body, how she liked and likes my attention to her and it, our shared fetishes, etc, and I thought about telling her about the douching-out, but didn't want to ruin the fun mood we were in.
You are taking advantage of a disability
Lucky guy. Moms are hot, I think at one time or another we all think about fucking our moms.