4 make trip to Hanoi for freed POWsCOPENHAGEN (AP) — Four militant opponents of the Vietnam war were en route to Hanoi today to bring home three American fliers the Communists have promised to release, The wife of one POW and the mother of another accompanied them.The group left New York Wednesday night. They were to stop briefly in the Danish capital and to arrive Friday in Hanoi for a two-week stay, according to the head of the delegation, Cora Weiss, cochairman of the Committee of Liaison with Families of Servicemen Detained in Vietnam.The POWs to be released are Navy Lt. Markham Gartley, 28; Navy Lt. Norris A. Charles, 27, and Air Force Maj. Edward Elias, 34.Accompanying Mrs. Weiss were Gartley’s mother, who is from Dunedin, Fla., and Charles’s wife, from San Diego, Calif. Elias’s father, who lives in Valdosta, Ga., said he could not make the trip.The remaining members of the delegation are David Dellinger, the other cochairman of Mrs. Weiss’s committee; Richard Falk, professor of international law and practice atPrinceton University, and Yale University’s chaplain, the Rev. William Sloan Coffin Jr.