There are new family-friendly Labor Day Weekend activities for the DFW area posted at frugalinfortworth.wordpress.com.
This weekend's edition lists a wide variety of suggestions...everything from Free Admission to the Nasher Sculpture Center in Dallas (plus a free walking tour of the Arts District) to a Blues Music Festival in the mid-cities area of DFW.
Here is the link to the list: frugalinfortworth.wordpress.com (click on "Frugal Fun ~ Cheap/Free Entertainment Ideas" in the right hand column if the weekend edition doesn't pull up immediately).
By the way, each Friday this free site posts cheap/free activities for the DFW area. They also post general savings ideas for the DFW area like restaurants and other savings tips...so you might poke around and see what else you can find if you are going to be in the area for a while and want to save some bucks.
Have a great visit to Dallas / Fort Worth!