The actress was joined by a few pals and hubby Cash Warren on Friday night at Sin City hot spot Hakkasan at the MGM Grand hotel, where the star was escorted with her group to the second-level private dining room.
There, the group enjoyed specialty gluten-free selections and sipped on signature cocktails.
They seemed "in good spirits [and] they laughed and engaged in conversation," a source tells PEOPLE, adding that immediately following dinner, Alba and her party made their way to the fourth level and sat at a VIP table located on the main stage, where they danced as resident DJ Calvin Harris spun beats.
"Confetti burst into the air [as cocktail waitresses] presented [Jessica] with a lovely three-tiered lavender birthday cake adorned with a number of pink cherry blossoms," the source says. "The birthday girl jumped out of her seat to get a closer look at the cake and was joined by [Cash] as they posed for pictures."
It was a special celebration for the mom of two, who was honored earlier in the day as Mother of the Year at the Helping Hand of Los Angeles Mother's Day Luncheon, where her daughters, Honor, 5½, and Haven, 2½, were on hand to see their daddy, Warren, present her with the award.
Reporting by MARK GRAY