Thank you for your very detailed response Chateaunole -du-pape. First of all, I love your name, Pope's New Castle. Our flight is at 9:00 from Atlanta to Montreal ( Delta) so yes an international flight. I know it isn't terribly early but since we need to be there three hours ahead of the flight and we are about a 40 minute drive from the airport, it is early for us. The flight was originally meant to go at 10:00 but was changed. Our TA has recommended to check into the International terminal.
Nice to hear from a fellow Georgian!