Hi,
Wow, your brave! Here are some tips to help you along:
leave middle of the night or super,super early in the morning so that your kids will sleep a good chunk of the trip
Get a "suprise" for each of them to open along the way----you could do coloring book with crayons, sticker book, treats, snacks, sm. toys etc. Tell them if they are well behaved and whatever else your rules are---that they can have it when they earn it. It will get them excited about earning the toy and the time will pass by alot quicker.
Get some kid CDs so they can sing along in the car
Wherever you stop, make sure you can get the kids out to stretch and run around--- if you can, plan to stop at MCDonalds or another ffood place because alot of them have jungle gyms or play structures---great for burning off energy.
I think this covers the basics--oh and one other thing-make sure that you are relaxed and calm before the trip. It will go a lot faster and smoother.
Good luck!
Molly