While half of Hollywood was at the White House Correspondents' Association dinner on Saturday night, the other (wilder) half was spotted at the Coachella Valley Music & Arts Festival this weekend. Joel Madden whisked his baby mama Nicole Richie and their daughter, Harlow, to the festival, where he deejayed at a festival pre-party. His brother, Benji Madden, brought his girlfriend (and Nicole's BFF), Paris Hilton, who also spent some time with her own sister, Nicky Hilton, and her beau, David Katzenberg. It wasn't just a family affair, however. Newly engaged Carmen Electra was also there with her fiancé, Rob Patterson, showing off her brand-new black-diamond engagement ring.