Party on! American flags were scarce, but there was no shortage of stars and stripes at mega-producer Joel Silver's annual Memorial Day beach bash. Festively outfitted celebs -- including Kate Beckinsale, Gwen Stefani, and Diane Kruger, among others -- flocked to Malibu, Calif., on Monday, May 27, to enjoy a fun-filled day in the sun with pals.

The family-friendly fete was especially entertaining for kids, who were treated to funny balloon sculptures like giant bananas, flower bracelets, and ice cream headbands. There was also a big slide on the beach, as well as a station where guests could silk-screen a pair of sunglasses or a peace sign onto a custom T-shirt.

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Stefani -- stylish as ever in a striped tank, white pants, red platform sandals, and a houndstooth jacket -- brought sons Kingston, 7, and Zuma, 4, with husband Gavin Rossdale, who was spotted chasing his boys around the beach. The No Doubt singer was less active, choosing instead to hang back under a huge black and white umbrella, but she kept a close eye on her kids in the pool. At one point, an onlooker tells Us Weekly, she came over to give them a bowl of cherries, and she and Rossdale exchanged tender glances.

"Gavin shot her a really sweet look," the eyewitness says. "And she looked back. It was a nice checking-in moment."

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Beckinsale, meanwhile, attended with husband Len Wiseman and daughter Lily, 14, who is the spitting image of her famous mom. Strutting into the party, the Total Recall star, 39, showed off her long, toned legs in a pair of striped shorts, which she paired with a sheer, cream-colored blouse and nude, ankle-strap heels.

Kruger and longtime love Joshua Jackson stopped in for a bit, too. A source tells Us they were "really cute" and "very lovey" during the bash, even while talking to Glee actress Dianna Agron, who attended with an unidentified male pal.

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Other guests included Sean Penn, Colin Farrell, Rob Lowe, and Great Gatsby actor Tobey Maguire. Minnie Driver attended as well, looking ready for summer in a white jumpsuit and matching straw fedora. She and her son, 4-year-old Henry, appeared to be having a great time as they made their way through the bash, sampling food and mingling with other families.

"She was so cute with her son," a source tells Us of the star, noting that she looked "fabulous." Adds another onlooker: "She was smiling when she came out of the party."

This article originally appeared on Gwen Stefani, Kate Beckinsale, Diane Kruger, and Others Party at Joel Silver's Star-Studded Memorial Day Bash: Pictures