Anonymous wrote:OP again. If this was a boyfriend/partner of a parent, would advice be different? Just curious.
LO is so lucky - already has a Grandma Bob, Grandma Sue, a Grandpa Rich and a Grandma Mary. (Not their real names at all, but you get the idea.)
Every family has its own cultural specifics about naming..
Mr. Steve is an odd choice in NJ, but a great one if your family has southern roots.
Whatever he would call another close adult friend is the model to follow.
Another path is grandpa in his ethnic tongue, if that differentiates.