I live in Dallas, and I can tell you - early in the morning, trying to get anywhere from the Airport is a really, really difficult thing to do. You'd probably want to stay around DFW - so you could go kill time someplace in Grapevine, Coppell, Irving... places like that. Although I'm not sure what would be a good time killer that early.

Where in town is your meeting? That would give the locals a little easier time trying to suggest things to do in the direction of your meeting.