Wow… sometimes questions go in a direction you don’t expect.
Of course it depends on the kid and the grandparents and whether they can handle it. I wouldn’t even consider sending a kid to an elderly grandparent who could not care for them.
I wouldn’t say there is comfortable familiarity with grandparents who live hours away. They have seen each other maybe 10 times ever.
If I had asked “at what age would you send your kid to summer camp?”, would everyone reply that it depends on the readiness of the kid and the reputability of the camp? That’s a given for me. I was really just looking for an average age, some things to keep in mind and maybe some anecdotes. Is 2 too young? Would it be too stressful (for the little one or the grandparents)? 3? 4? 5? Out of diapers? Already attends preschool/kindergarten? What cues would you look for to determine whether the kid would enjoy a few days away with grandparents?
My oldest is almost an adult now. He visited my parents several times, but I don’t remember at what age that began.