Tomorrow (Saturday, August 20) from 10:00 a.m. until 2:00 p.m. there will be a free Pier 5 Family Field Day, with potato, sack, and Hula Hoop races, parachute games, soccer skills lessons, and scrimmage games. More information here.On Sunday afternoon, August 21 from 2:00 to 5:00 the Nantucket lightship (photo), docked at Pier 6, near the foot of Atlantic Avenue, will be open for free public tours. More information here. At 4:00 p.m. there will be a special treat for kids, as Brian Floca, author of Lightship, reads from and discusses his book. More information here.Monday, August 22 is the 100th anniversary of the National Park Service, and there will be a day and evening long celebration at Pier 1, with guests from …