This is a super tough one for me, so I answered other.
I know they want me to call them mom & dad, but I just can’t do it. I love them, but they are not my mom and dad. Therefore, I call them nothing, and if I have to address them and my DD is with, then I’ll call them Grandma Jean and Grandpa Steve. If my parents are there, then I will call them just Jean & Steve. If nobody is there and I need to address them, then I will approach them and just start talking. Rarely will I call for them from across the room. The whole thing is just so awkward for me. When my DD gets married the first thing I’m doing is telling her new husband to please call us by our first name, unless THEY want to call us mom and dad. I/we will respect whatever they want to do.