Often, an older couple has already bought everything they need, and you find it hard to buy gifts. If you do not want to buy anything unnecessary stuff, take a gift of art ... fun art. Caricatures can be embedded into the details of their life fun along. If a couple has a strange or funny behavior, it is easy to embed the image.
All children can buy a caricature together, so you do not have to come up with any single gift. Take a look of my portfolio: www.caricaturegifts.net/portfolio