We have made several trips over the years with small children. Make sure you bring plenty of things to keep the kids occupied in the car. A popular one with my kids is the color magic books and markers. The nice thing about these is the markers cant get all over your car or the kids. I made activity bags for my kids. Usually a tote bag with crayons, coloring books, a couple of dolls and matchbox cars. A laptop desk also comes in handy for the kids to write on. We have also brought a portable dvd player so the kids could watch a movie here and there. My kids also brought their leapsters and gameboys.
I always enjoyed the ride with my kids in the respect that it gave us time to just talk as well. General conversation about different places we see on the road always helped to pass the time. My little ones like going over the bridges so we would always be on the lookout for bridges. The other that I liked is audio books. I found these helpful when they just start to get tired and lay back for a nap. Listening to stories relaxed them.
The other thing is make sure you keep a first aid kit handy in the car with band-aids, children's painkillers and children's dramamine in case of car sickness, headaches, or cuts.
That is all I can think of for now. Hope it helps some. If I think of anything else I will post it. Good luck on your drive!!