Debbie,
There is a memorial to Edith Evans at St. Ann's Episcopal Church in Sayville. She and her sister Lena spent their childhood summers there after her father's death at the home of their grandfather, Israel Corse.
Smithtown was founded by James Clinch Smith's ancestor, Richard Smith. There is a memorial to him at St. James Episcopal Church in St. James.
Marshall Drew's family was from Greenport, but I don't know if there is anything left there to see.
Albert A. Stewart had a summer home in St. James, and he was said to be a friend of Mayor William Gaynor of New York. The Stewart home is gone, but the mayor's home, Deepwells, is still standing, and is sometimes open for tours. It may interest you because he was mayor at the time the Titanic sank.