Head to the King Center, and spend sometime exploring the exhibits. Be sure to leave in time to catch the free afternoon tour of MLK, Jr.'s house, showing up early enough to be one of the fifteen let in.
Head to Busy Bee for lunch (which just happens to be on Martin Luther King, Jr. Street), one of the most famous black-owned restaurants in Atlanta. Chow down on the famous fried chicken and home-cooked veggies, people-watching all the while, before grabbing MARTA at Ashby Station and taking it to the Dome stop.
Walk fifteen minutes to the new National Center for Civil and Humanitarian Rights, if only to peruse the collection of MLK, Jr.'s correspondence and other private papers, a collection inherited from Morehouse College.
Skip Centennial Park, but walk down its Drive to The Varsity and bask in this inner-city, fluorescent wiener-paradise. "Naked dogs" are available for those who don't want cole-slaw or chili on their dog.
As it's getting late, call for an Uber back to the Highland Inn, a quick nine-minute trip by car. Since it is Saturday evening, make plans on attending a church service at the Historic Ebeneezer Baptist Church the following morning.
If there's still a bit room left for dessert, stop into Soul Vegetarian No. 2 for a scoop of soy ice-cream (a great way to placate vegans who might have been disturbed by the Varsity). Read some of the literature laying around about the interesting story of the Black Hebrew Israelites, a decidedly different take on the African-American experience than the narrative the day was spent exploring.