George Clooney and Amal Alamuddin have already started the celebrations.
"The Monuments Men" actor/director and his new fiancee toasted to their engagement with a party at Cafe Habana in Malibu on Sunday, according to several reports.
The longtime bachelor, 53, and the British human-rights attorney were joined by U2's Bono, the Edge, and model Cindy Crawford and her husband, Cafe Habana owner Rande Gerber, People and Us Weekly reported.
"George seemed sweet with his fiancee," an onlooker told Us. "I saw them kiss once, and he had his arm around her the majority of the time. They looked very happy."
The group congregated on the restaurant's patio, did some karaoke and toasted to the couple with wine and tequila, People said.
"After the toast, George and his fiancee were all over each other," a source told the mag. "Lots of hugging."
It seemed to be a relaxed affair, with the 36-year-old bride-to-be wearing a glittery neon tank top paired with floral shorts and a blazer and Clooney sporting a casual blue polo with jeans.
News that the "Argo" producer popped the question surfaced late last month.