What a fabulous piece of writing! It was very touching that you had such a good vibe with your grandma, and that you two understood each other so well. And even though she is gone and you don't have much time with your Dad, you can at least spend time with your Mom and try to build memories with her.
You might also enjoy writing the details of some of the memories you made. You could talk about how they made you feel and the things you liked most about them. Then years from now when your own memory begins to fade, you can read them and refresh the details in your mind. There are many things I wish I'd written down, so that advice comes from experience.
"Kudos!" for a really good post! I like the way you write, so genuine and down-to-earth. 😊