Gigi! I love it! When my granddaughter, now 15, was born, my son asked me what she should call me. I asked him to give me some time to think about it.
A day or two later I told him I had narrowed my grandma name to two choices. One was Gma, the other was Oma. He asked why those names. So I told him that I'm used to answering to those names already. In response, he said "Well, GEE, MA!"
And I said "I rest my case."
He chose Oma. Later, I found out that Oma is the German version of Grandma. Even later, I found out that the Greek version of Grandma is Ya-Ya! which I would have chosen in a second if I knew about it.
Enjoy those grands - they grow up even faster than our kids do - but you already know that!