WASHINGTON (AP) — Five years after then-Sen. Barack Obama spoke at the groundbreaking ceremony for a monument to Martin Luther King Jr., President Obama will speak at its dedication.Obama, first lady Michelle Obama and daughters Malia and Sasha made a surprise visit to the memorial to the slain civil rights leader Friday evening.The president and first lady will host a White House reception for the King family and members of the civil rights community in the afternoon after Sunday's ceremony.The dedication of the memorial on the National Mall was originally scheduled for August, but was postponed after Hurricane Irene swept through the Washington region with high winds and heavy rain.