Kevin Federline headed to Las Vegas last weekend with the kids, as his estranged wife, Britney Spears, continues to stay on in rehab.

Kevin went to Los Vegas for a paid appearance at the Mirage hotel & Casino lounge Revolution.

“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.”

When Federline arrived in the city with his two boys – Sean Preston, 18 months, and baby Jayden James, 6 months, he was accompanied by a nanny, his mother and brother, as well as two bodyguards.

He was late for dinner with friends and family at the hotel’s Japonais Restaurant because he wanted to tuck his kids into bed. However, by midnight he was seen relaxing at the VIP table at the Revolution with a group of friends which included comedian Jeff Beacher.

Federline’s ordeal with Spears rehab has helped to mature him. A source is quoted as saying “He wakes up with a purpose each morning and has enjoyed his family being around him”.