Hi again L.!!
Do you by chance have a bunch of old photographs of your parents beginning from their courtship and then throughout the years? Or maybe just a bunch of photographs of your whole family - all their kids, grandkids, etc.?? Kodak Gallery online has these awesome photo books that you can create (meaning maybe you can create it for your dad) and you can pick the backgrounds, journal in the books and make captions under all the photos. They are very neat, unique, and sentimental and would make a wonderful gift to your mom, especially if it were just pictures of the two of them throughout the years. And I know several other online photo places are doing books like this as well. Heritage Makers is one. I made books like this for Christmas gifts of my daughters first year of life, they were gifts to her grandparents, god parents, and other close relatives. They loved them! And I will most likely do one similar for their 60th anniversary party. The books are easy to create, you simply upload the photos into the website and drag them where you want them, write in any journaling you want to say. You can chose up to 9 photos per page on the big books or do a 100 photo book that is 5x7.
This is the only thing I can come up with. My dad always bought my mom a bottle of bourbon or something that of course was only going to get consumed by him! But he also did surprise her with nice jewelry. :-) Good luck!!
-Char