A portable DVD player is a good idea as well. You can let them watch their favorite Disney movies as you make your way to the parks!
Best advice, travel at night as much as possible. With all the drivers you have, that should not be a problem. You travel when the children are naturally sleepy.
DVD players are a must with about two dozen movies and also cartoons, and take headsets or ear buds. They make a controller that can be used with a DVD player that actually lets the kids play simple video games on the player, I have one.
If the kids have hand held games such as Game Boy or a Duel Screen, take them along. You can use rechargable batteries or you can buy a car adapter.
Take small multi use toys for the small ones, like Leap Frog toys.
Play road games with the older children, adults included. Two we always played, were looking for license plates from all the different states and countries. Split the car or cars your in, into two different teams and make some kind of reward for the winners. This game can last the entire trip.
The second game was counting cows, yes cows that are along the Interstate, you'd be surprised how many there are. Each team counts the cows on their side of the car. One catch, you lose all your cows if there's a cemetery on your side of the road and you have to start all over again. But you do set a limit on the total number of cows, like 100 or 500. So everyone is looking for cows or cemeteries. Also make some kind of reward.
And for the grown-ups, you can always entertain the kids by singing the old standard "99 bottles of beer on the wall" Take kid songs on a cd, and sing along with them.
Being from Pennsylvania also(about 60 miles Northeast of you), that 1050 mile trip from Mount Carmel to Florida can be a hassle with children. During the daytime, stop about every 1 1/2 to 2 hours. Take about 1/2 to 1 hour food breaks and also a 10 to 15 minutes gas stop.
Like I said before, I've been through this at least 15 times, and when you break up the trip into small hops. it's not to bad.
Good luck with this one.
Walt Disney World's Magic Kingdom
Disney's Animal Kingdom
Disney's Hollywood Studios
Disney California Adventure
Universal's Islands of Adventure
Universal Studios Florida
Universal Studios Hollywood