Caught in the Act!

Plus: Rihanna celebrates her assistant's b-day, Kate Hudson & A-Rod and more

Photo: Denise Truscello/WireImage

• After a late-night 21st birthday bash at Tao Las Vegas, Rumer Willis followed up the festivities with a more intimate celebration the following evening: She held a family dinner at Koi inside the Planet Hollywood Resort & Casino. Joined by dad Bruce Willis, his wife Emma, mom Demi Moore, stepdad Ashton Kutcher and her sisters Tallulah and Scout, the starlet pre-selected dishes from the restaurant’s menu for the meal. The group – which also included family friends – assembled in the Fountain Room for the private feast, which ended with Rumer blowing out all the candles on her cake after a “Happy Birthday” serenade.

• Before coming to Vegas to celebrate with Rumer, Ashton and Demi hung out with close pals Soleil Moon Frye and her hubby Jason Goldberg at a Modart magazine party at L.A.’s Thinkspace Gallery. The happy couple sipped on red wine, browsed the artwork and hung with German street artist Nomad.

• In the Big Apple, Rihanna celebrated her assistant’s birthday with a bash at Buddakan. The singer and her pals were all decked out in party hats. “She sang ‘Happy Birthday’ with the whole crew and everything,” a source says.

• Continuing her baseball-themed road trip, Kate Hudson teamed up with her New York Yankees star beau Alex Rodriguez for dinner at San Francisco’s Epic Roasthouse. The two grabbed a back corner table and cozied up over oysters, caviar, filet mignon, a whole fish and some sides.

• Michelle Trachtenberg, chatting up revelers at a dinner celebrating the Web site Shopbop.com at New York event space The Smile. “She was super-social,” a guest says, adding that the actress talked a lot about fashion. “She was totally the life of the party.”

• By ALEXIS CHIU, JENNIFER GARCIA, MARK GRAY, LESLEY MESSER and ULRICA WIHLBORG

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