As spiritual and secular advisor to the Kennedys, Father Cavanaugh also performed other rites for the family. On April 24, 1954, for instance, Cavanaugh performed the marriage of Peter Lawford and Patricia Kennedy at The Church of Saint Thomas More in New York, New York. Some of the 250 guests at the wedding reception at the Plaza Hotel included Greer Garson, Marion Davies, Bernard Baruch, Supreme Court Justice William O. Douglas, Mr. and Mrs. Igor Cassini, and Mr. and Mrs. Morton Downey Sr. He was the personal priest of the Kennedy family and a good friend of John F. Kennedy's father, Joseph Kennedy. John Cavanaugh was Virginia Joan Bennett's preferred celebrant for her wedding to Edward Moore Kennedy in 1958, but Rose and Joseph Kennedy chose Cardinal Francis Spellman instead.