DH and I are taking my 85-years-young mom for 5 nights at BWV in May. It will be her first trip to WDW so everything will be new to her. We plan to do things like the 3-D movies, live shows, parades and fireworks in each of the parks. My mom is in very good shape for her age so we plan to take her on a few rides such as the riverboat, Pirates, Haunted Mansion (if she can handle getting from the moving walkway into and out of a doom buggy), maybe even Soarin' if she's feeling adventurous, Maelstrom, the boat ride in Mexico, etc. -- all gentle rides.
I'm thinking she also would enjoy the Carousel of Progress, given that she personally experienced many of the different stages of "progress" during her lifetime. We plan to do "Walt Disney - One Man's Dream" at MGM, again because she will remember a lot of the things on display there. We're planning to eat at the 50's Prime Time for similar reasons.
We also plan to have dinner one night at AKL. DH and I have stayed there a few times so mom has heard a lot about it. I want her to see it for herself. We also plan to tour a few other resorts since I think she will enjoy seeing all the theming -- the Grand Floridian, YC and BC (since they are just the other side of the lake from BWV), and WL come to mind as places my mom would enjoy seeing. I think she will enjoy taking a ride on the boats that go between some of the resorts and nearby parks. (I love that boat that goes from the Grand Floridian and MK -- I think my mom will, too.)
I haven't really started planning our trip yet, so these are just off the top of my head. I'm very interested to see what other people have to suggest on the subject of taking an 80-something to WDW!