I like the ideas you already have, Kim...especially the picture with a matte that can be signed by all the attendees.
I agree with Bonnie that the party, itself, will be the best gift...especially if you can invite friends or relatives they don't often get to see. When our daughters did a surprise 40th anniversary party for us, I really enjoyed getting to see people I hadn't seen in a while.
Do your parents still get around OK (i.e., go to the grocery store, beauty shop, etc.)? If so, gift certificates to restaurants or services (haircut, manicure, pedicure, massage, cable TV or satellite TV...whatever) are always nice.
One of our friends at our party gave us a basket with champagne, pretty glasses, and a scented candle in a cute little holder. The daughters gave us money for and made arrangements for us to change to Dish Satellite with DVR (TIVO) services. It was a great party!
I know how hard it is to get something for someone who doesn't want for anything or need anything. My DH's 80th birthday is coming up Friday, and I have no idea what to get him.