Hi,
I would suggest you include different textures as well as items for repetative actions. Satin, rough, etc, as well as a flap with buttonhole and large button. Different type pockets with a button closure, zipper closure, even a ribbon that ties it closed would be great. Items need to be big enough so hand with arthritis can still manipulate them. The different textures, such as satin are very soothing. My mom lived 8 years with Alzhiemers, I wish I had made her a lap blanket like this. Good luck with your project.