MY FAMILY OF FOUR is looking out at Lexington Battle Green in Massachusetts, where “the shot heard round the world” was fired, igniting the Revolutionary War. As our local guide, arranged by the lovely Inn at Hastings Park down the street where we’re staying, describes what the scene may have been like, I glance at my children’s faces. They are attentive and engaged, connecting the dots of names (the midnight riders including Paul Revere!) and events (Boston Tea Party!) they’ve heard before.