I have a horrible time with this each year. They never want anything, particularly anything and are trying to get rid of a lot of things as they downsize. What I have done in recent years is give them a gift certificate to a B&B or a restaurant that they like. I've thought about signing them up for a fruit of the month club, but haven't tried it. They also like it when I make a donation to a charity in their honor. UNICEF has a great setup where you can donate vaccinations and other things for children. There are also websites where you can give the money and let the recipient pick the charity.
my parents tell me not to waste my money on them and if i get them something they get mad, except for when i was a kid in school and made things for them.