Federline on March 24
While his ex Britney Spears worked on her dance moves
back in Los Angeles, Kevin Federline celebrated his 29th birthday over the weekend in Las Vegas with his kids and ex-girlfriend Shar Jackson.
Returning three weeks after a visit there with the kids
while Spears was in rehab, Federline arrived in town Friday afternoon with sons Sean Preston, 1, and Jayden James, 6 months, in tow.
After checking into Caesars Palace, Federline spent the remainder of the afternoon relaxing in a VIP cabana at Caesars' Venus Pool Club, a private, somewhat hidden topless pool adjacent to the general-public pool, a source tells PEOPLE.
The birthday festivities kicked off Saturday night, with Federline (who turned 29 on March 21) starting his evening at Social House, dining on Asian fare with 14 of his closest friends and family by his side, a source tells PEOPLE.
"He was talking on the phone and texting the whole time," said the source.
Later, Federline made his way to Caesars' Pure Nightclub, where his ex Shar Jackson was already present.
"As soon as his parents got to the club they immediately went to Shar's table on the other side of the club and hung out there for a while," a source says. "They were taking photos with her and catching up. It's pretty easy to see that they still care about her."
Meanwhile, a well-dressed Federline "was clearly having a good time, hanging with his group and singing along to most of the music," says an onlooker.
Drinking Jack Daniels, Federline hung out in his VIP area most the night, waving to the crowd as they yelled for him.
At 2:30 a.m., Jackson again returned to Federline's table to dance with his parents. Federline then grabbed the mic, says a source, and said to the crowd: " 'My entire family came out for my birthday. My brothers are here, my mother, my father, my sister and even my ex Shar Jackson came out for this.' "
Just before 4 a.m., Federline retreated to his room at Caesars, the 4,000-sq.-ft "Rain Man Suite" – where, yes, the movie of the same name was filmed.