It’s so difficult I just don’t know what to buy them. They have everything they need. If your saying this then don’t worry there is an answer.
The point is they don’t need “stuff” they have plenty. Their house is full of it if they are like my grand parents .
However what they value are memories especially ones with their children and grand children. Why not arrange a memory book for them by contacting all the family and getting everyone involved. To save time you can all arrange to contribute photos and time to collate the photos into some kind of story. Weddings, Christenings and even holidays together. It’s great to sit at a computer with photos on screen but it’s not the same as a book. A special gift they can pass on to their great grand children. It will have all the best photos of that frozen moment in time. The first step, could be birthday parties and christenings. Each photo has a story to tell and it will bring back happy family gatherings for them. They will appreciate the time spent to produce it just as much as the gift.