Kevin Federline takes the kids to Vegas

 KFed might not be the biggest looser after all

While Britney Spears remained in rehab, Kevin Federline headed to Las Vegas last weekend – with the kids.

Federline was in town for a long-planned paid appearance at the Mirage Hotel & Casino lounge Revolution, sources tell PEOPLE.


"Kevin was really low key," one source says. "You could definitely tell he was on his best behavior. He was having a good time, but wasn't the wild, crazy Kevin who used to come to Vegas.He arrived on Saturday with Sean Preston, 18 months, and Jayden James, 6 months, plus a nanny, Federline's mother and brother, and two bodyguards, sources say.

He had dinner with friends and family at the hotel's Japonais restaurant, says a source, who adds: "He was late for dinner because he wanted to tuck his kids into bed.By midnight, he was relaxing at a VIP table at the Revolution with a group of friends who included Las Vegas comedian Jeff Beacher. Spears' rehab ordeal, says a source, has matured Federline.

He wakes up with a purpose each morning and has enjoyed his family being around him," says the source.

A rep for Federline declined to comment.