Noticeably absent? Owen Wilson, the actress's on-again-off-again beau. Not that the party – at the home of Hudson's mom, Goldie Hawn, 63, and her partner Kurt Russell, 58 – lacked for a jaw-dropping roster of A-List guests, including Demi Moore, Ashton Kutcher, Justin Timberlake (though without girlfriend Jessica Biel), Matthew McConaughey, Tobey Maguire, Jessica Alba, Cash Warren, Gwyneth Paltrow and husband Chris Martin, Gwen Stefani, Eva Mendes, Adam Sandler, Zach Braff – even Cher!
"Kate was elated, dancing all night, having the time of her life – and she looked amazing in a very sexy little dress and [Christian] Louboutin heels," a source tells PEOPLE. "She gave a very touching speech and spoke about how important her family is to her."
Justin Life of PartySo who contributed to getting the crowd into a festive mood? "Justin Timberlake was the life of the party," says the source. "He was dancing, drinking Don Julio tequila, and he had everyone doing the 'electric slide' on the dance floor."
Another partygoer "was even twirling Kate and Goldie around on dance floor," says the source.
As for the other revelers, "Eva Mendes kept a low profile, hanging out mostly with Zach Braff and Cash Warren in the beginning of night," says the source. "And Adam Sandler came by very briefly to say happy birthday and grab a cupcake, while Cher spent the whole night dancing, of course!"