CC...
I was discussing your situation with my wife. You will be flying in on a domestic flight and definitely will not be in the same terminal as your next flight to Mo'bay. You will have to get from your domestic terminal and gate to the tram and take that to the international terminal and go to your departure gate. If your Memphis to Atlanta flight is on time you should be able to make it. I would suggest getting your seats as close to the front of the plane as possible so you can be the first ones off. Remember....your luggage has to change planes too. The airport shouldn't be bad on Thanksgiving day as most people will already have traveled.

My wife says while your situation is doable......she would play it safe and take the later flight. Good luck with your decision.