This is a bit of a two-edged sword. They remember good and bad experiences. And it does not need to be some great trip to the amusement park to be memorable.
As much as I despise my MIL, I would never say anything bad about her to my kids. But they noticed things on their own. Since she had my husband when she was barely 20 and my parents had me when they were over 40, my parents were always the old grandparents. My mother had spent one of those awful rainy cold April days when they try to play Little League games at the ballpark watching my two oldest play through multiple rain delays about nine months before she died. Fast forward a year, and my MIL comes to visit. She spent most of her time shopping for her other grandkids and helping my husband’s brother work on his house. She was at our house when it was time for the oldest boy’s game and he asked if she was going. No, she had some shopping to do. After the game, my son wondered if his grandma didn’t come to his game because she didn’t like him, and brought up his other grandma coming with her cane in the rain and this game was even sunny. I muttered something about my mom liking baseball and maybe his other grandma didn’t but he knew the score.
My father’s parents died before I was born so I only knew one set of grandparents. While I know they took me to an amusement park from pictures, I don’t remember it. I do remember my grandpa taking me on his morning routine. We would walk two or three blocks to a little business area. He would stop at the bank, stop in the drugstore and get a newspaper, and stop at the bakery. When we visited, he always bought these vanilla layer cakes with too much frosting that I didn’t like, but would pretend I did cause it made him happy. But I also remember my grandma giving me my first Barbie when I was 5 and needed surgery. All my other dolls were hand me downs but she gave me that doll when I was scared and they had to pry it away from me when they put me under.
So I guess this is my long winded way of saying be part of your grandchild’s life, that is what they will remember. If distance is a problem, Zoom them regularly and find out what is going on in their lives that is important to them. Know them well enough to know how to support them and show them through your actions that you love them wholeheartedly. Never play favorites with them.