No matter what, it'll be a crap shoot, that's what having kids is. Both kids could be awesome on the drive, either or both could be terrors. One factor is sun - even if you have some sort of sun guard over the rear windows, they can get hot (or even sunburnt) sweaty and miserable. Last time we drove down with an infant (6 month old, with her sister nearly 4 years old), we did it during the night to minimize their being awake, but we wound up seeing (not being a part of, just seeing) the results of some graphic accidents, so now my wife is paranoid about doing too much of the drive at night. We also got hit with some overnight construction that pushed us back 2 hours.
At the same time, the last time we went (when kids were 2 and just past 6), we tried to time the trip to avoid DC traffic but not middle of the night, with a hotel booked in Savannah for the night, and we got stuck behind so much traffic, so much construction, so many detours, as well as needed bathroom and lunch breaks, cleaning up car sickness, etc., that 7 hours into the trip, we were averaging driving about 35 miles per hour, then had to speed and scramble to make our overnight hotel, about 11 pm.
So now we're stumped about what to do. Kids don't know this but we're planning a brief December trip as well, so any money we can save on one trip can go to the other. But then there's the hassle, or at least the potential hassle, of the drive down, something we're all already anxious about instead of looking forward to. Even the kids, who have an ungodly amount of entertainment options while we drive (dvd players, amazon fire tablets, kids' innotab tablets, books to read, activity books, etc.). But we can't find a flight in our budget, at a convenient airport, with all the other cards lining up we need to have lined up to make work.
So hey! Good luck!
