Good starts. Must start somewhere. We all want an electric car and a lack of charging stations is a problem. Therefore I would vote for starting with parking lots, they are closer to cars.
Big-box store roofs are much cheaper to install on than building elevated racks in parking lots. Electric power is easily delivered where it is most useful via wires. So, for cost-effectiveness, the first place to put solar is on those big flat roofs. But customers do like covered parking lots.