Nothing wrong with doing it in one day if you both are up to it. As long as you aren't driving while half asleep no issues, I think its easier to make it down in one day (to SC) than to split the trip up. Less travel time = more leisure time! One thing that I wont travel without now is a 12volt cooler, we pack it with sandwiches, drinks, fruit, pizza just about anything. Now we only stop for a restroom break and have enough cool food to last 2\3 days of driving.
As long as you aren't pushing your limits and can still function the more power to you, but there is nothing to fret about if you are exhausted and need to stop for the night. I've often met a number of good people by stopping at the next KOA or Mom & Pop camp ground for an evening of recharging my batteries!