Create a self-contained buried treasure game that your kids can do together. In "Bottled Treasure," you fill a 2-liter bottle or other plastic container about three-quarters full with rice or birdseed. Then add a variety of small household objects such as paperclips, buttons, marbles and different colored toy Army men. Be sure to keep track of how many objects you put in and what they are. Most importantly, seal the container tightly so you don't get rice or seed all over your car.
Your kids can then shake the bottle and try to find all of the treasures you "buried" in the bottle. If you've got a long trip ahead of you, they can also guess what the objects are. Once they've found everything on the list, reward them with a treat, like choosing the music for the next hour.