My BFF and I take several road trips a year. Between the 2 of us we have a 9 yr. old boy, 2 7 yr. old girls, and a rowdy, probably ADHD little 3 year old. We stop every 2 hours at a park or restaurant with a playground for snacks. We have things like nuggets and parfaits and apple dippers. If we are in a park we usually break out the fresh fruit and juice boxes. Kids don't process time like adults. They just feel the discomfort of their hiney's, the need to go pee, the extreme boredom, the monotony of the highway scenery, etc...
Along with the kids being more physically and mentally able to get back in the vehicle we also have the break and feel better and more alert when we resume the trip.
She bought her kids individual DVD players and they pack in the movies. She bought splitters so that when they put on the headsets to hear their movies other kids can add headsets too. She also brings their DS hand held games and any other items the kids can hold in their lap and use. I bring books and Barbie's, and coloring books and crayons.
If we are in a hurry and don't make the regular stops we KNOW IT. The kids start bickering, they start doing silly, ornery, things like banging each other on the heads with empty water bottles, or just silly things like getting the 3 year old to say "You're goofy" or other not so nice things that aren't bad just not what I want to hear.
One thing we have found, when she had her Venture Warner's Brother edition van and the DVD player was built in, don't take movies you can't stand to hear over and over and over and over...the sound track to many movies will just be annoying and drive you nuts...hence the portable DVD players and individual headsets in her new van.
So, to enjoy a road trip with kids:
Stop often, they need to move and run, more stops only need about 30 minutes each for RR breaks and running around. Full meals need more time for running and playing plus eating.
Have snacks avail. in the vehicle and also at the stops, have a mini picnic.
Remember to keep their mind's busy
Space the kids so they have lots of individual space. Put toys in a bag on the seat in front of them of beside them. Have some variety.