Few kids would say no to a pocketful of cash (even if it's fake!). Gather a gaggle of friends from the neighborhood and challenge them to a game of Guess-timation.
You'll need to do a little prep work first. Before the game begins, take a trip to your local grocery store and buy fifteen common items: a bag of carrots, a carton of juice, a tube of toothpaste, a can of shaving cream, and similar things kids might have in the house on a regular basis. Be sure to keep the receipt—you'll need the prices!