Word Chain
Begin this game from the Party 411 website by first coming up with a category. Categories like "animals" or "movies" work well. Pick a player to say a word that fits within that category. After the player says a word, the next player has to state the first player's word and add his own word. Throughout the game, the players have to restate the words that came before and add their own words to the "word chain." Anyone who cannot remember the words in the right order, or who cannot come up with a proper word fitting with the category, gets eliminated. The last person remaining wins the game.
Colors of the World
Try playing this game from the Do It 101 website by first picking a color. Select one player to start the game. She has to look outside or within the vehicle and pick something made of the chosen color. For instance, if you picked "red," she can point to a red car or a red flower bush along the road. Any player caught lying about what they see gets eliminated from the game. Once a player contributes something he spotted, the next player has a turn. Change the color when you run out of options. The game continues until only one player---the winner---remains.
Road Trip Scavenger Hunt
When planning a road trip past some scenic areas, play this scavenger hunt game to keep the kids engrossed in their surroundings. Before you head out to your destination, make a list of some things you have a strong chance of seeing along the way. If, for instance, you plan on driving through a big city, think of some historic or popular sights the children can see from their seats inside the car. If driving through San Francisco, write down the Golden Gate Bridge on the list. Hand the lists to the children when you get in the car. Tell them to pay close attention throughout the trip and mark off the things they see from the list. The person who spots the most things on the list wins the game. If you don't mind the snapping sounds of a camera, have the kids take pictures of the things they spot to ensure no one cheats.