Who is het up about it? They just asked for some options to explore.
Let's see, you started an internet thread about it, they've rejected the usual options, and asked you to come up with others? I'd say that was already pretty over-invested.
Plus as I said, it will become second names for them, so I understand if they want something they like, not really irrelevant if it’s
A name that you get called regularly by multiple family members for the rest of your life?
It makes as much sense as those parents on the Baby Names forum who are already determined that their little Elizabeth will be known as Beth, not Betty, Liza, or Liz, before she is born.
In my experience grandparents can decide what they want to be called, but the children will ultimately decide. It's up to the people in question, obviously, whether they want being called Grandma or whatever to be the hill they die on with their grandchildren.