For the Car Ride:
1- CAR DVD PLAYER.
This is my #1, and there's a reason it's bolded, capitalized and underlined. They make great distractions for children, even if it's only for an hour, that is one hour of undistracted driving for you. The set I have is two dvd players that hook into each other and then strap onto the headrest. They also have jacks for headphones so that you don't have to be distracted by the movie.
2- Snacks:
I make a variety of snacks, including fruit, veggies, and crackers and package them into individual serving baggies so I can just throw them into the child's hands and they can get them out. Juice Boxes make it easy, or you can use spill proof cups.
3- Books, Toys and Games:
Don't bring little board books or thin books either. Bring those Dinosaur Encyclopedias or everything about animals. Give them something that will keep them engaged for a long period of time. Magnetic games are great in the car!
4- Pillows and blankets:
If you've got an especially long ride ahead of you, you'd be surprised at how boredom and the power of suggestion (just having the blanket and pillow in the car with them) will allow for a snooze or two along the road.
5- Kids Tunes:
Because you can't always listen to what you want. Bring ones that you enjoy as well, to make the process easier. I highly recommend the mixes above.
Overall, be prepared to stop, be prepared to hand them things but at least you'll be able to make it easier on yourself!