Long story short - we are expecting our first child and hold traditional values, so would like grandparents to have grandparent names.
My MIL has a grandchild already and he calls her something very unique/different that doesn't resemble a grandparent like title at all, it's more of a nickname.
I'm totally ok with whoever else in the family calling her whatever they want and respect that, but for us, we would like to go with something traditional. I'm concerned that this might cause upset for not only her but my B/SIL. I don't want to look like I'm 'insulting' what she is already called.
She isn't a young Nan so it's not an age thing, and she wouldn't have minded being called Nan/Grandma, if she wasn't asked if she would prefer that or to choose something different for herself.
DH agrees, but I want to avoid offending in laws if I can.