Oh, as far as DL availability between ATL and MIA, have them check all sorts of crazy connecting routings on all partners, including flights into FLL (well, it's quite improbable that CO will have anything anywhere around the holidays). I did manage to put together a DL flight through CVG once when I needed to get to Miami for Copa over the holidays. It's like pulling teeth, however.

Also look at Copa's Orlando schedule. It's less frequent, so I don't know if it works on the connections. But it's a shorter drive for you! Finally, consider the counterintuitive approach of grabbing a flight NORTH to JFK on DL and taking the new Copa JFK-Panama flight. My guess is that ATL-JFK flights are easier to get a x-mas time than ATL-MIA, so it might be worth the detour.

Good luck!