Keep some sweets in the car For Example Wine Gums, Haribo's, Mints etc. It's less hassle to by sweets without wrappers and your not forever finding wrappers hidden around the car. Plus it also stops the hunger until your next pit stop.
Make a Stop! Plan your journey to have at least one stop which is on the way to your destination but also entertains you all. It can be something that last for 20 minutes or a few hours, It's good to get out and stretch your legs - even if it's a quirky roadside attraction.
Keeping entertained by listening to music, playing the all time favorite game of ISpy With My Little Eye or watching DVDs.
This helps to keep children's minds off of the journey time and concentrate on something else. Plus it can be quite fun for you as parents as well.