There are many options. First you can remote mounted the handles for the tub and/or shower so he can't reach them. You can use an electronic valve which might be beyond his ability to operate (sometimes it's beyond mine). I would consider a floor drain as a fail safe system with a water alarm. A water alarm is a simple device like a smoke detector that has two contacts. If the contacts come into contact with water the alarm goes off.

Offsetting the controls is fairly common maybe not in residential world but can be done by a good plumber. I wouldn't call it special needs. I would just call it learning differently or something like that. We all have different styles and paths of learning the term "special" over the years has a different and negative connotation. I think differently abled is better. Not to be a big PC lecture but words and terminology do matter especially to ones self worth.