Well My mum is only 38 ( had me at 17), Shes just had a little baby girl..even though I was due before her GRRRR!! lol
So she definetely doesnt want Grandma or Granny, Shes not keen Nana but doesnt mind Nanny.
I called mine Mammar..
MIL parents will be called Grandma and Grandad because there quite old...lol