Andrew, things will change greatly with the birth of a baby. Depending on how the baby travels, and how your wife is handling being a new mother, you may or may not be able to do a 14-15 hour trip in a day. It will take longer than it would pre baby as you will have to make stops for feedings, changings and crying.
People all handle new babies differently. Having 2 children, I know I personally would not have enjoyed a long car trip at that age. Though, thankfully they do sleep quite a bit.
October is pretty in the Smokies, though I have no idea how far it is from Witchita