Most American's do not celebrate Grandparents Day. Even though this is an American Holiday. Ours is in September.
When I was a child in the late 70's and 80's, our school would do a spaghetti lunch for the Grandparents that could come in to the school. That is it. The extent of celebrating Grandparents Day in the US. I have never even seen a Hallmark card for Grandparents Day, but I am of the generation that does not buy/send tree killing cards, so maybe they have them now? 
Like any holiday, if you want to and have a good relationship with your Grandchildren, by all means go ahead. But please remember my post in that it is not that big of a holiday in the US either.
I agree with the PP who said if it is painful due to estrangement, do not invite it in. That is what I have done with my mother and it works for me and the children. For us, there is no need to celebrate someone who was a horrible mother and grandmother.
We all have a choice of celebrating holidays. FWIW, I also ignore Valentine's Day and St Patrick's Day and Columbus Day.