So then the only option would be the AA Arrivals Lounge (BA ATL flights arrive at T3)? I guess that's better than nothing. Our departing would obviously be out of T5 the next morning.

Also, since we only have half a day to really do anything, I'm guessing there are plenty of cheapo hotels at the airport, right? Best to pick one at the Airport/Terminal or one just outside? Adding cab fare, would it be a wash to just staying onsite?