George Clooney and Amal Alamuddin's engagement becomes official after they hosted a party for family and friends on Sunday night at Cafe Habana in Malibu. The "Monuments Men" star definitely looked like he's so smitten with his British lawyer fiancee but he's reportedly not taking a back seat when it comes to preparing a prenup.

"People got a show they didn't expect and other [restaurant patrons] said it was the best Mother's Day ever," E! News reported, citing a source.

Among those in attendance in George Clooney and Amal Alamuddin's engagement party were Cindy Crawford and her husband, Rande Gerber, who owns the restaurant. Bono of U2 also went to wish the soon-to-be married couple good luck.

The British attorney showed off her long, lean legs by wearing floral shorts while the "Monuments Men" actor was very casual in a blue shirt and denims.

Prior to George Clooney and Amal Alamuddin's engagement party, however, the "Ocean's 11" producer suggested a prenup agreement in order to protect his estimated $200 million net worth if ever they do separate. And the pretty barrister agrees with the proposal, the Star reported.

"[Amal] is a very smart woman who understands the business side of a relationship...She wouldn't expect anything less," the insider added.

Another source told People that George Clooney's girlfriend is "a very accomplished attorney." She isn't someone who is pursuing a career in acting or entertainment. She's on his level," the source added.

Although most people only know her as the "George Clooney girlfriend," barrister Amal Alamuddin is a specialist in human rights, criminal law, international law and extradition proceedings. She's was also named London's hottest barrister for 2013 and represented Wikileaks founder Julian Assange.

George Clooney was also spotted with his new fiancee dining out at Nobu in Malibu, California on Thursday night.

Amal Alamuddin showed off her new ring to former model Cindy Crawford who joined them for dinner, along with Academy winner Edward Norton, according to Entertainment Tonight.

Just before their party on Mother's Day, the actor's representative kept mum about the George Clooney and Amal Alamuddin engagement when prodded for a reaction on the then rumor.

The said representtive only told the website: "I don't comment on my client's personal life."