There are so many things that can be said about this. I chose grandma because everyone else wanted to cutsie names so they would not sound old.
My mom was called Meemee as is one of my neices not that she GB's. My aunt was called mama by all and my uncle was daddy tom to all.
Granny is a friends of my and mema is another. For a while my nephew called my grandma gumbo. Pick what you like or be grandma until the little one decides what they want to call you.