This isn't a complete answer. However, you might want to look into a Wii (?). From what I have seen on the news, some retirement homes have them for their senior citizens and they help keep them active.  The Wii won't be a strenous workout, but it might give you some variety, and, from what I understand, it will be a low impact workout, which might be good for your joints (from what I read in your post).