Gwen Stefani & Gavin Rossdale
Todd Williamson/Invision for Prevu/AP
07/02/2012 AT 06:00 AM EDT
Wrapping up an all-day shoot with No Doubt on Thursday, Gwen Stefani
concluded her night at Siren Studios in Hollywood with family.
Joined at the venue by hubby Gavin Rossdale and the couple's two kids, Zuma and Kingston, the clan checked out Steve Erle and Pete Black's Exposure 2 exhibit, hosted by Prévu sparkling liqueur.
"Gavin wouldn't start walking around without holding Gwen's hand," an onlooker tells PEOPLE. "They couldn't have been sweeter. They were playing with their kids the entire time and [seemed] so doting. Kingston was embarrassed getting his photo taken. It was very cute. Zuma was laughing and his dad was holding him."
Meanwhile, Lauren Conrad
made her new relationship with rocker William Tell public at the event, as the two were "walking around holding hands," the source says. "There was a long line [to get into the event] and the couple didn't [seem to] mind waiting in it. They were laughing the entire time and were so cute." – Jennifer Garcia