Similar boat. I actually had this conversation with my own mother when my first child was born. I had always called my grandma by a nickname, and she asked if we were going to have our child call her (my mother) by the same nickname. I told her that it's up to what the kids call her, and that I wasn't going to force a nickname on to the kids. To me, that was what I did and it stuck. I don't see why I need to push my kids to call someone one thing or another. My wife's family doesn't do that, and there aren't any issues. However, I think there's still some level of resentment from my parents when I took this stance. Kind of like they felt disrespected.