Both couples placed their hands over their hearts as taps sounded near a U.S. flag at half-staff before greeting Kennedy relatives, including some who arrived in Obama's motorcade.
The day of tributes began at the White House, where Obama awarded the Presidential Medal of Freedom to 16 living and deceased Americans for their contributions in fields ranging from sports and entertainment to science and public service.
"These are the men and women who in their extraordinary lives remind us all of the beauty of the human spirit, the values that define us as Americans, the potential that lives inside of all of us," Obama said.
Hillary Rodham Clinton, daughter Chelsea Clinton and film director Steven Spielberg were among scores of people seated in the White House East Room for the ceremony, which Obama said is "one of my favorite events every year."
Kennedy established the modern version of the medal but was killed by Lee Harvey Oswald in Dallas on Nov. 22, 1963, weeks before he was to honor the inaugural group of recipients. Hundreds of notable figures since have received the honor.