When you have younger children who are learning their colors and numbers, your fellow drivers on the highway can provide the perfect opportunity for them to practice. Come up with fun, yet age-appropriate challenges like being the first to find five green cars or 10 semi trucks. Engage older children with guessing how many of a certain type of vehicle you'll see in 10 minutes. Let the winner choose the next DVD or hour of music.
If you're traveling with teens, make the game a bit of a surprise. Have everyone in your family choose a color and when you find 10 vehicles of that color, you have to provide a reward for the family. Whether it's dessert at dinner or a family activity like mini-golf, it's a way to engage older kids who may want hide behind their iPods and cell phones during the trip.