The Battery is home of the Atlanta Braves with cute shops, restaurants, and things to do year-round. You can park in the red deck for up to 2 hours for free.
The beltline runs through midtown Atlanta. It provides a great walk with some very trendy stops. I would recommend potentially parking at and checking out Ponce City Market. From there you can access the Beltline directly.
For a more laid-back vibe, visit Marietta Square. You will find several local businesses and a market on most Saturday mornings.