Like Gord said, definitely use reinforcing in the slab. Wire mesh at a minimum. Since it'll be open to the weather, you don't want it to crack. Even though you're in Arkansas, you'll get freezing temperatures at times which will open any cracks and make them much worse, and will expose the reinforcing to corrosion. Basically, you're building a concrete driveway, but with a roof. Reinforcing wire and thickened edges are cheap insurance.
