There are a few possibilities, depending on what time you leave in the morning.
You can check the halfway point first:https://www.trippy.com/halfway/Atlanta-and-Cincinnati
But it looks like there's not much at the exact midpoint, and it's suggesting Knoxville for restaurants like Dead End BBQ
and The Tomato Head
That would normally work if you were okay getting into Atlanta in the evening, but I think the main constraint is making it to Atlanta by 3pm.
If you use the road trip planner, change it to "1 day", and then hit "customize this trip", you can remove a bunch of stops since you're mostly driving straight through:https://www.trippy.com/drive/Cincinnati-to-Atlanta-in-1-day
Here's one possible itinerary:
6:00 am: start in Cincinnati
drive for about 6 hours
11:51 am: Chattanooga
stay for about 1 hour and leave at 12:51 pm
drive for about 2 hours
2:38 pm: arrive in Atlanta
So if you focus on Chattanooga, that might fit better with your schedule. You can browse all the suggested restaurants in Chattanooga to see if there's an option you like:https://www.trippy.com/popular/Restaurants/Chattanooga
I would recommend barbecue if you like it, since there's probably some interesting places, maybe Sticky Fingers Smokehouse
or Sugar's Ribs