Dr. Joseph LeDoux is planning a party in Eunice as a chance to chat with his friends here and entertain them. A 1967 graduate of Eunice High School, LeDoux returns to Eunice often, but will hold a homecoming event at 4 p.m. Sept. 7 at Gabrielle’s. He will be accompanied by his friend, Colin Dempsey, an Irish folk singer. LeDoux , 75, is a recently retired professor at New York University — profess…