Hi Larry:
It sounds like you have a wonderful vacation planned. Without knowing more about your family, I would lean towards
Epcot over
Animal Kingdom for your third full day at the Parks. My family loves both parks, but as a disclaimer, Epcot is my favorite of the four Disney World theme parks. As objectively as I can look at it, most people wouldn't argue that the is more variety and more to do at Epcot. At Epcot, my family always takes in Spaceship Earth, Living with the Land, Soarin' (our three-year old just reached the 40 inch height requirement), Turtle Talk with Crush, the Seas with Nemo & Friends, the attractions inside the Innoventions pavilions (my boys are currently obsessed with The Great Piggy Bank Adventure), and the Kim Possible World Showcase Adventure. We also tour the countries of World Showcase. Highlights of World Showcase are the Kidcot Fun Stops, which are craft stations where your children can draw and color while learning about different cultures as they interact with Cast Members from around the world.
Since you are staying at
Animal Kingdom Lodge, you'll already have some exposure to the animal theme. Even if your room does not overlook a savanna, there are plenty of spots sprinkled throughout the Resort to animal-watch. Of course Animal Kingdom Park is more than just animal-watching, but at the end of the day, I believe Epcot will likely give your traveling party more variety and satisfy more tastes.
Enjoy your vacation.