You know elderly people just need company. When you are with them, just sing, just play with them, crack jokes and bring them food or have food with them. Talk something, which is of interest to them. They are not interested in listening to wisdom from you or learning any new techniques from you. Don’t behave like a teacher, more knowledgeable with your elderly parents. Casually, you may give few words of wisdom. Observe if they are absorbing it. Otherwise, just being with them is good enough. The most important aspect not to forget to smile with them, as no one oversees your happiness except you!