I just did the 77/79/95 for March Break - drove myself and four teenagers down to Disney and I was the only driver - have driven this several times before - total driving time about 18-19 hours, but total trip time there was about 24 hours as we hit some horrible traffic jams on the I-77 due to an accident and on the I95 due to bike week in Daytona and March Break traffic - May should be a breeze for you. I rented a station wagon from Budget and had unlimited km which was great (Dodge Magnum we rented). Lots of room for the teens and they had portable dvd players and cd players to keep them busy. Stopped when we needed to for gas and pee breaks - never worried about safety as all the rest stops are beautifully kept and have security all the time. Have slept in them before with my hubby when we didn't have the kids with us for at least four hours and never had a problem. With four teenagers though, I stopped just north of Charlotte NC the first night after eleven hours, then we were in Orlando the next early evening (would have been sooner without traffic problems). If you break it into two days, you can leave early in the morning the first day, stop just at dark so you're in the mountains in daylight, then continue the next morning - very pretty drive and the kids love the two big tunnels we go through under the mountains. I wanted to try the i75 for something different, but the kids just wanted to get there quick, and since I was the only one who could drive, quicker was better. And the only major centers you drive through are Charlotte and Jacksonville, so the roads aren't busy enough to stress you out in between, and the major centers are short and easy as well. Have a great trip whichever way you decide - getting there is the best part!
Tracey