While there are no doubt countless places to go in the downtown area, a place I would recommend to you is Cool River. It's an upscale bar/lounge that's not far from the airport. There's a resturant section as well as a large bar, with a lot of tables as well, and occassionally a live band playing. I've been there a few times and it's a very nice place. If you're cabbing it, it's much cheaper than driving into the downtown Dallas area. As time gets closer, bump this thread up and if you are interested in going there, I'll give you directions. It's very, very easy to get to from the DFW airport area.
One other recommendation I would make is, if you a big fan of meat (this has been posted here before), is to eat at Fogo de Chao. For dinner, it's generally around $45 a pop (like $28 for lunch) so it's not cheap, but my oh my is it good stuff, and you can eat however much you want until you're stuffed. That place is in Addison, probably 35 mins or so from the airport, but very easy to get to. I highly, highly recommend it for at least one meal while you're in town.