Cameron Diaz

and her family held a memorial service for Cameron's dad, Emilio Diaz, this weekend, and two of Cam's ex-boyfriends showed up to lend their girl some support.

Justin Timberlake and John Mayer arrived at Mahe in Seal Beach separately, and paid their respects to Cam, along with the other guests who came to honor her dad's free-spirited life.

"Most people started arriving at 1:30 and hardly no one wore black," says a source."Lots of people were wearing Hawaiian shirts. It looked more like a party."

The boys stayed until about 4, when most of the guests began to leave, and after Cameron had made a speech about her late father, who died suddenly of pneumonia last week.

If you want to show Cameron that you care, the family has suggested sending donations to Surfrider.org or Reefcheck.org in Emilio's name, in lieu of flowers.