Inside George and Amal's All-Star Engagement Dinner

George Clooney and Amal Alamuddin (@X17online.com)George Clooney and Amal Alamuddin have plenty of reasons to celebrate and they did just that, with a handful of celebrity friends, on Sunday.

[Related: George Clooney Is Engaged to Amal Alamuddin]

Fresh off a Mexican getaway, the newly engaged pair brought their love fest to Malibu, where they were feted at Cafe Habana by the restaurant's owner and Clooney's business partner Rande Gerber and his wife Cindy Crawford, as well as U2's Bono and The Edge.

The "Monuments Men" star, 53, and the human rights attorney were casually dressed for what was described by several news outlets as an engagement party on Mother's Day afternoon. He had on a black polo shirt and pants while she rocked a bright green skull T-shirt with a pink bow appliqué and patterned shorts. They both had on aviator sunglasses, which they removed when they were settled in with their friends. Of course, Bono kept his shades on the entire time, because, well, he's Bono.

At one point, Clooney was seen resting his hand against Alamuddin's back. The pair mingled together with the group and also separately. At one point there was a toast to the future bride and groom.

Rande Gerber and Cindy Crawford were there -- and so was Bono. (AKM-GSI)

A couple diners tweeted about seeing the star-studded group at the restaurant. One person joked that his mother, after having a Mom's Day cocktail, gave a high five to the Oscar winner:

And another patron was just excited to be seated next to such big stars:

Another onlooker tweeted that Anne Hathaway also happened to be dining there and noted that she came over to say hello to Clooney.

Alamuddin was sporting that emerald-cut diamond engagement ring, which her fiancé helped design, for the festivities. They left carrying flowers and gifts. (See more pictures of George and Amal on X17online.com.) Crawford also walked out with a bouquet of red poppies.

[Related: 5 Things to Know About George Clooney's Bride-to-Be]

The pair has been in celebration mode since confirming their engagement in late April. Last week, they were in Cabo San Lucas, where Clooney owns a home next door to his Casamigos Tequila partner, Gerber. People magazine reported that the trip was to celebrate the wedding of Clooney's longtime pal, actor Thom Mathews.

Soon enough, however, the wedding festivities will be for Clooney and Alamuddin. According to multiple reports, the engagement won't be a long one. By fall they should be man and wife.