My mother-in-law is very generous when it comes to giving my children money. It usually comes in the form of $5 or $10 bills inserted into holiday cards or in person during the twice-a-year visits, at which time she chooses to hand them money in a covert way; a sheepish attempt to hide the fact that she's spoiling them. During a recent visit to the local grocery store, my 5-year-old, carrying one of these $5 bills, passed in front of this display of miniature cars that read "4 for $5." He was...