Working on Harry Hines in the evenings?
I presume you're going to be driving, although there is some fair train service in the area, especially in Los Colinas. Just about any airport would work, but I would personally choose one to the south because the area north and west of where you need to be has a lot of toll roads. That's just my personal peeve, I do not like toll roads. Even if they don't have rental car on site, Enterprise will pick you up almost anywhere.
There's no train service within walking distance of any of these
KRDB (Dallas Executive) - looks like $10/overnight fee, but they say they waive it with fuel purchase. Fuel currently $4.75.
KGPN (Grand Prairie) - no fee? $5/night? $10/night? better call. Fuel at $4.54
KGKY (Arlington) - $10/night, waived with fuel purchase. Fuel $4.44
KHQZ (Mesquite) - $10/night, waived with fuel purchase. Fuel $4.35
KLNC (Lancaster) - no fee, Fuel $4.33. But this is way out there, you'll think you're lost getting to the airport.
Fuel prices from skyvector, fee informatin from rampfee.me
I would avoid any of the 3 airports that form your triangle, their fees are substantially higher. Although it might be worth paying the landing fee at DFW or DAL if you can otherwise travel on the train.