Mike Leonard is a lucky man. It's not everyone who gets parents like Jack and Marge. At 87, Jack is a pathological optimist with an inexhaustible gift of gab. Marge, Jack's bride of 60 years, though cut from the same rough bolt of Irish immigrant cloth, is his polar opposite, pessimistic and proud of it. What was their son, Mike, thinking when he took a sabbatical from his job with NBC News so he could pile these two world-class originals into a pair of rented RVs and hit the road for a month?