I agree, don't let it be a big thing for you and DH. You may well find that your kids decide this for themselves anyway.

I call my parents, who DS sees regularly, granma and grandad. DS calls them "gee-gee" and "do-do". And DH's parents are "gee-gee bok-bok" and "do-do bok-bok" (the bok-bok is for the chickens at the place we were staying when we visited DH's family last year)
My parents wanted to be called OB1 and OB2. I will leave it to your imagination to figure out what the OB stands for... I was not impressed.

So anyway, the moral of this story is, you never quite know what you might end up with.