Talking of keeping the kids under control in the car, we have a number of car games we invented (or modified). It was all thanks to the frequent long car trips to get the kids to and from school, or to choir practice or performances. Or dance classes & performances. Or anything else.
1) Marg Spotto - we had to modify what to look for andalso had to have a mental list, not one on paper. So OUR list (feel free to modify your own) is:
big dog
small dog (must be half the size of the big dog chosen by the same person)
tall tree
short tree (rules as above)
emergency vehicle (lights must be flashing for more advanced players)
car licence plate ending in player's age
(for advanced players, the licence plate must also include player's initial)
Add in whatever else you need.
The original Spotto game (as distributed by BiPolar (BP) petrol stations in the 60s) had a printed list which included level crossings. Trouble is, too often the railway line didn't extend farenough. And these days we don't have level crossings except in more remote areas in the country, mostly out west. None south or on the coastal strip, until you go farenough north for the cane trains to be crossing the road (north Queensland) and that's a bit off our beaten track.
2) For high school students - find elements of the Periodic Table as well as any compounds, in the licence plates. More junior players can use them as acrostics.
3) The alphabet game. Warning - this can get noisy.
The aim of the game is to find consecutive letters of the alphabet in shop signs. No two players can use signs from the same business, even if there are multiple signs. No two players can use the same sign. You can't advance until you have found the previous letter. As with all other games, the driver is the adjudicator, no arguments.
Junior players are permitted to use signs on moving vehicles (such as advertising on buses). REALLY junior players may use street signs. Older players are forbidden to use street signs unless they are advertising. So a sign saying, "Powerhouse Museum this way" is not permitted for older players. But the "Powerhouse Museum" sign IS permitted.
Once the player gets all the way through to "Z" (pizza parlours are much sought after) they begin again, IN REVERSE. And yes, that means finding yet another pizza parlour, gozleme or similar.
This game is best reserved for driving in the city, it's good even when in gridlock.
4) Sherlock Holmes.
The aim of this game is to try to identify the personality and interests (and anything else) of the owner/driver/occupant of an adjacent car. It's a team sport, everyone in the car works together. This is a good game when everything else is getting dangerously competitive.
Example - thee car next to us in the gridlock is covered in wet leaves. Conclusion - the car is parked outside and the driver has left from nearby, spent the night nearby.
Or - the car is covered in brown mud in multiple layers.
Conclusion (current one only) - the driver lives in our village and works outside "on te mainland". Currently all our locals' cars (the commuters) are covered in mud in layers. We can't wash cars too often with the strict rules we have; besides, why bother when you're only going to get the car muddy again on the drive home?
You can determine a great deal about the driver of a car, from what you see inside and out. A neat suit coat on a hanger - appearance is VERY important in his job, he could be an airline steward or a hotel concierge.
His coat is neatly worn on the back of the driver's seat - he could be a doctor, a policeman (look for insignia) or a salesman.
His coat is lying on the back seat - he's got the morning off work, or maybe the day off; he only needs the coat occasionally and he's alfready senior enough in the company to not need to worry too much about the occasional crease. Or he's a back room manager, the sort who gets the job done quietly and efficiently without a lot of public appearance.
There's a crochet rug spread neatly on the back seat - he's driving his mother's car, he probably lives at home.
There's a vinyl sheet spread neatly across the back seat of the car - he owns a large dog.
And so on.
Some fantasy is permitted - again, the driver is the adjudicator.
These are good games for kids in so many ways, especially the last one.
Warning - if you have a Pervasive Developmental Disorder (PDD) kid, they could find this last one a big struggle. Don't let them flounder, but also explain the reasoning where you can. Help them think in these very unusual (for them) directions and it WILL benefit their social skills.
One final warning about this last game - keep the volume down. The last thing you need is for the driver of an adjacent car to hear what you and your kids could be saying about him. You mightn't have time to utter the word "conjecture".
Marg
That story bout killed me. 
