The Gloucester Stage Company hosted its annual summer soiree the other night, and the benefit extravaganza featured a performance of playwright Athol Fugard’s coming-of-age story, “Master Harold . . . and the Boys,” followed by a reception during which cast members Anthony Wills Jr. and Peter Mark Kendall entertained guests with three songs: “Ain’t Misbehavin’,” “Angel Eyes,” and “All of Me.”