Do your family vacations turn into one long whine-fest when you refuse to spend $30 on a Graceland key chain? On your next trip, let the kids be in charge of the budget. They want to spend big bucks on dinner and hotel pay-per-view their first night in town? Fine. Just be sure to ask them how they plan to pay for day two. When all they can afford is water and a nature walk, they'll learn "real world" math mighty quick.