There are many things you can plan to do with your grandfather. Plan activities with your grandpa that give him a break from his routine. Do not remind him of his health problems. You could, for example, take him for a drive or head to the beach with a picnic basket.
Another thing that you can do with your grandpa in the outdoors is
going fishing. It is an activity that allows him to enjoy your company.
If you are old enough and your grandpa enjoys an occasional drink, it would not be a bad idea to take him out for a beer. He might open up and tell you funny stories about his past, making it a fun time for both of you. Steer clear of topics like religion and politics, as the conversation could explode into an argument.
When going out becomes difficult, grandpa may not mind a swim in the family pool. It is important to have somebody around to keep an eye on him while swimming. If it is raining, indoor games, maybe a card game or a board game, with the family is a fun way to spend a few hours.
Cooking could be another thing to do with your grandpa. Sharing a meal together will help the two of you bond.