I'd go for Nonni, it would probably be one of the first sounds baby will make! I was always Mamaw until the grands got closer to school age, starting around 3 or 4 I began calling myself Grandma most of the time, and by the time they were in school, that is what they called me. Once in awhile they say Mamaw. My grandma refusd to be called Granny, same for my Mom, and I didnt like it either. My MIL went by MIMI to her daughters kids and grands, but my children called her Grandma Dell. My sister's G-grands called her Grandma-great.