This is a topic that I'm always learning more about - especially as my little ones are growing! I thought I would share with you the tips that I have so far.
Pack a special backpack or bag for each child, with crayons, book, toys, activity sets, stickers, handheld games.
Pack picnic food so you can stop to eat where the kids will have room to run around.
Allow enough time for rest stops. Taking a break every two hours of driving time is a good pattern. You can expand the drive time as you kiddos get older. I like to bring bubbles, balls, frisbies and other fun items to provide a little play opportunity at rest areas.
Burger King and Mc Donalds have great playrooms on major highways. If your little one doesn't have problems with eating while riding in the car, let the kids burn off energy while you order food "to go" to eat later in the car.
Public school (if not in session) or park playgrounds offer a free way to stretch legs. Once we came across a free splash pad park. We had some unexpected wet clothing but it worked out great!
Surprise younger kids with some new surprises, given out in intervals. Don't give them everything you have all at once because they will tire of it all quickly.
Books on tape are entertaining and the public library is a great resource to borrow some.
In case of younger children's need-to-go-now emergencies, consider bringing a portable pottie.
Bring a small cooler for cold drinks and fresh snacks to save money and eat healthy.
Have your little ones wear shoes that are easy to get on & off. That way they can feel less restricted while riding in the car.
I always make sure that I have the following in easy access: wet wipes (for cleaning), paper towel, kleenex, extra cloths, small blankets, towel, lots of healthy snacks and beverages, camera, and water/beach toys (incase we stop near water).
Let the kids follow along on a map.
If staying at multiple locations pack your clothing needs by each location/day. That way you wouldn't need to haul all of luggage in and out of the "hotel" for just a one night stay.
If you have the resources to do it safely, drive through the night while the kids are sleeping. Just make sure your not passing any of the fun sites you want to visit while they are closed and the kids are sleeping.
My daughter had really bad motion sickness problems when she was little so we had some extra things to help her: DVD player, towels covering the back windows so she couldn't see the movement, an allergy medication that our pediatrician prescribed (helps with motion sickness), extra clothing and cleaning supplies, a bowl incase she got sick, and we had to stop OFTEN! Thankfully she outgrew that.
I would love to hear what tips you have! We are planning a couple of long road trips this summer so I am looking for some new ideas.