"Ladies! Dorothys!" yelled Mary Shriver at nine dark-haired young people. She is one of the producers of "WiZaRD," an upcoming off-Broadway musical loosely built around the music of "The Wizard of Oz." It was 9 a.m. on Thursday at the South Street Seaport, and the nine women were sitting on benches about 100 feet from a makeshift stage, which was built between a schooner and a mall. The bright-eyed actors carried bottles of water and cups of hot coffee, and some even wore pigtails.