I am now 67 and never hardly knew my dad's parents (mum's were dead when I was born). She did not get on with her MIL. I saw them only a handful of times as they lived a few hundred miles away. They died when I was 10 and 12. At that age, I did not miss people I did not know, thankfully.
Later, as an adult I moved to where they had lived in my dad's old home town. From my cousins there, I found out about them and was very unhappy that I never knew these lovely people. I have pics of them which I found after my parents died, which had been hidden away from me all my life. It was exciting but poignant to discover my dad as a child in many photos with his parents (they had the luxury of having a camera in the 1920s and 30s!) I had assumed that there were not photos considering the times they lived in.
So, even if you are estranged from her and the GC now, later I think they will want to know you as they get older, as another poster said, and your son will be able to arrange that. Give him photos of him with you together as a family when he was young to share with them. Tough, if 'she' does not like it, there is nothing wrong with doing that.
Take care and look after yourself hugs