When traveling with children, give them each a $10 roll of quarters for the trip there. They pay you a quarter for asking how much farther, fighting with their sibling, whining, bad attitudes, etc. At the destination, they get the keep whatever is left for spending however they choose.. It also built teamwork because they were negotiating with each other ("I'll pay to ask how much farther this time, if you'll pay next time" type stuff)