PDK in Atlanta has the Downwind restaurant (bar and pretty good cafe style food) in the old tower building on field, and the 57th Fighter Group restaurant (WW2 theme, good food, bar side and fancy dining side) right next to the airport. Bar side of the 57th has an outdoor patio right next to a taxiway, and the Downwind has seating where you can look down on the ramp and the central part if the airport. PDK is/was the second busiest airport in the state, so lots of business and GA plane traffic to see. There is also a concrete slab outside the bar at the 57th where they sometimes park a P-40, a DC-3, or some other warbird, and a yellow Waco used to pick up air tour passengers right from the patio area.
McCollum Field (RYY) in Kennesaw has a chop house restaurant on the north side ramp area. Never been there but I saw a lot of folks eating there, and heard the food was good. Kennesaw has a train museum and Kennesaw Mountain Civil War Battlefield National Park nearby too. There is also a Stearman biplane tour company at RYY.