A father-son duo — from the same Brooklyn cult family linked to murders and phony, pan-handling nuns — was charged in a fatal shootout at a Queens baby shower, a law enforcement source said. Expectant grandfather Lagarthucin LeGrand and his son Lagarthucin Jr. were among seven people indicted for the apparent gang-related May 4 shooting in Richmond Hill, where more than 40 people, including kids, were at the gathering, Queens DA Melinda Katz’s Office said. Great Neck resident Jefari Dobie-Reinhardt, 24, was killed and three others hurt amid the volley of gunfire, according to authorities, who said at least…..