S.B.
I struggle with this every year! SO I can definitely relate. My husband's grandparents love getting Sam's Club memberships (unfortunately, my BIL always gives that, so it's taken in our family).
The bed desk went over well with the Grannies in our lives. It's basically a tray that goes over their lap. The top can adjust to tilt and there are pockets on the side to store things. They use it when writing letters and doing bills. My Granny keeps stationary and postage stamps in the pockets. She says she loves being able to sit in the living room and write comfortably while watching her soaps. I bought one today at Bed Bath Beyond. With my 20% off coupon it cost me $25.
For the Grandpa last year we got him a Bird Song book. It tells you about a bunch of different birds, you punch in a number and press a button and then you can hear the bird call. We weren't sure how it would go over (He isn't really a bird enthusiast). He seems to really enjoy that book, especially when the grand babies come over because they like to look at it with him.
We have done gas cards too. I know gas is cheap right now, but all the grandparents seem to obsess over the cost of gas.