If your memories with him are good ones, why not compile a collection of memories? Ask family members and friends to record something that made them laugh, or an account of a special occasion with him. Add in pictures of places that mark parts of his life, souvenirs, stuff like that. You can do it in a scrapbook or as a video.
A friend of mine recently asked all her Dad’s friends, going way back to old school chums, to record a short video, and then she edited it together with pictures, for example, of the house he was born in and the playground of his primary school. It took her a bit of time and some travelling to get all the pictures, but the end result was a very joyful celebration of his life. I’m sure it’s better to do that while someone is still around to enjoy it. Too often we save our memories of people for their funerals.