I am thirty… When my grandparents were still around I would refer to them as Grandpa and Grandma or Gramp or Gram for short. I was fortunate to have several grandparents and one great grandparent in my life, I miss them very much. Depending on the grandparent I use to use nicknames for them when I was younger, but was always respectful. 

I haven’t had children, but I can somewhat relate to wanting to appeal to the younger members of the family. I am an uncle to six kids and although all call me uncle, I don’t mind if they simply call me by my name so long as their respectful. I have similar relationship with one of my aunts in that I often call her by name without calling her aunt first. I think as long as there is respect there really shouldn’t be an issue, but it also boils down to the individual. As for me all I want from my nieces and nephews is to be respected and someone that they can talk to if need be.