You can also arrange with a college campus to offer a class during the day and maybe built for senior adults in something stimulating such as learning to write stories. Music and painting are great sources of courses.
And because, we cannot over-emphasize, be sure that you always spend some of the time you are visiting actually in stimulating conversation with your parent. Just like the brain development of young children, the older adult brain clearly responds to being stimulated by important and new information, albeit linked to ideas already learned. Do something more with conversations and take these conversations into the world outside. Just walk slowly (or push the chair) in quiet places, stopping and talking and moving on, while allowing your parent to give opinions or even advice. Show that you value the opinions. We think that although that some things change with the times, parents can carry the beliefs that we need to hear. If not, the person can be respected.