Birthday Girl Britney's Big Night Out
But first, she helped NBC ring in the holiday season.
Spears (wearing a coat that covered her sexy party dress) taped a special greeting for the opening moments of Wednesday night's star-studded Christmas in Rockefeller Center 2008 (airing on NBC at 8 p.m. ET), then headed to the top of Rockefeller Center for a quiet dinner at The Rainbow Room with her father, Jamie, manager, Larry Rudolph, mom, Lynne, and sons Jayden, 2, and Preston, 3, a source tells PEOPLE.
Afterward, Spears ventured downtown for a combined birthday and album release party at the club Tenjune. Guests at the Big Top-themed bash – a nod to her new album, Circus – included Tyson Beckford, Jeremy Piven and Lance Bass.
One star who didn't make it in? Ugly Betty's Eric Mabius, who was turned away from the jam-packed club when he arrived with an entourage of friends.
Next up: Spears returns to L.A. where she will reportedly help light a 52-foot digital Christmas tree at the new L.A. Live entertainment complex Thursday night.