Put a stop, at least temporarily, to the "Are we there yets?" with Surprise Balls: wads of aluminum foil that have been wrapped around special items, such as candy and small toys. At certain milestones (every 50 miles, say) toss one to each kid.
Make sure at least one contains a written directive: "Pull over and change seats," "Stop for ice cream," and so on.
Both the treat and the wrapper will keep kids occupied as the foil is great for twisting into fun shapes.
