You'll be in terminal D and if you have to spend 2.5 hours landside, I'd do it at the bar in the Grand Hyatt (which is open to all, not just guests). Heck, my co-workers and I often meet there for happy hour when we are all arriving back at DFW fairly close in time to each other. At that hour of the day, the lounge should be somewhat lively and its a nice place to decompress until you can check in.