By SARA YOKLEY United Press Staff Writer NEW YORK, April 20 Mrs. Douglas A. MacArthur wore a chic maroon hat and a huge white orchid Friday but it was her smile that won New York.The general s lady looked as though she never had enjoyed herself more than she did Friday.Seven and one half million persons lined the streets of New York to see the general and his wife drive by and not one saw her when she was not smiling.She was proud of her husband and son and showed it; she waspleased by the spectacle of New York s biggest parade and let everyone know it. Oh, it s very nice, she told reporters who wondered when the strain and her public appearances would begin to tell. I enjoy all of it. Mrs. MacArthur held up better than the general. At City Hall, his hand trembled as he saluted and later he leaned on his aide for support, but she remained fresh and sparkling. Her movement! were quick and sure andshe waved a white handkerchief gaily at the crowds.Alongside his vivacious mother in the car, 13 year old Arthur MacArthur seemed shy. His face almost was blotted out by the peak of his air force cap and big sun glasses.Like any mother, Mrs. Mac Arthur took no chances on losing her son in the crush when they attended the ceremonies at City Hall and kept a watchful eye on the boy.The orchid she wore was given her by a very dear friend, Mrs. MacArthur said, and her bouquet of roses were from her hometown Murfreesboro, Tenn. I ll be going there real soon, I hope, she said.Mrs. MacArthur wore a maroon wool dress, a black sealskin jacket and simple pearl earrings and a pearl bracelet. Her son wore a maroon jacket.The last time the, MacArthurs were in New York 14 years ago they were on their honeymoon.How did it feel to be back? Wonderful, the general s lady said. Wonderful. Generals Vivacious Wife Wins All New York With Smiles