Right in the middle of Downtown Dallas is a wonderful park with free community events happening every day! They also have food trucks to choose from and a little water feature for the kids, so it's easy to hang out here for a few hours.
This is a great area to explore and get a feel for regular Dallas life! There's lots of vendors that come out on Saturday mornings, but you can also just hang out and try good food, look at shops, and walk around downtown.