My 70 year old parents have been to WDW many times over the years, and really enjoy it. My dad claims he is not a ride person (however, last year he went on Space Mtn and Big Thunder Mtn for the first time and said he loved them!!

).
Anyway, before discovering my dad liked Space Mtn, my parents have really enjoyed the Animal Kingdom, especially the slow-pace of the walking trails in Africa and Asia. They also love to meander around the World Showcase at Epcot, watch the films, try some different foods, etc. Spaceship Earth and the Living Seas are also interesting for the older folks.
In the Magic Kingdom (which they only go to if they are with the grandkids), my parents really enjoy the Pirates and the Haunted Mansion. These are not traditional rides and they really enjoy the attention to detail, especially in the Haunted Mansion. Also, a must see is Mickey's Philharmagic. This was a big hit with both my parents AND my husband's parents (who went to WDW for the first time this winter). My folks also enjoy It's a Small World.
MGM is probably our least favorite park, but it does have shows (not rides) that may be enjoyable for your dad. Also, lunch at the Brown Derby will make you forget you're in a theme park (complete with table linens and a piano player).
Have fun convincing him to go.
