DESC: Most parents do more harm than good when they try to teach their children about money. They make saving seem like a punishment, and force their children to view reckless spending as their only rational choice. To most kids, a savings account is just a black hole that swallows birthday checks.David Owen, a New Yorker staff writer and the father of two children, has devised a revolutionary new way to teach kids about money. In The First National Bank of Dad, he explains how he helped his own son and daughter become eager savers and rational spenders. He started by setting up a bank of his own at home and offering his young children an attractively high rate of return on any amount they chose to save. "If you hang on to some of your wealth instead of spending it immediately," he told them, "in a little while, you'll be able to double or even triple your allowance." A few years later, he started his own stock market and money-market fund for them.Most children already have a pretty good