Electronics are also out of the question (most of the time), my grandparents have a tough enough time figure out how to navigate through a cell phone and stuff like that. You probably don't want to get clothes either because it's definitely hard to find the right style. Of course there are exceptions, I am just using my own experience as an example right now.
So is there anything that all of us can relate to? Food? Maybe, but you're not going to wrap some food in a box right?
Here you go Grandma, Merry Christmas!
Yeah that's awkward.
I think what I will buy is maybe like... a Christmas carol CD, or a cassette tape (lol), or maybe even a CD with some songs that they like. Surely they have CD players, and they KNOW how to use that! Of course there are different types of grandparents, different types of personalities, so do what you think is right! Think about what they know and will enjoy, and try to suit their needs.
Something like this maybe!
Either way, some people may like it, some people won't. In my case, I am pretty sure it is appropriate. Who knows, maybe for your grandparents they want a new fishing rod or something! In any case, happy shopping!