Sean Preston & Jayden James Federline: Off to Europe!

The Circus is traveling abroad - and so are Sean Preston and Jayden James!

Kevin Federline's longtime attorney tells E! News that K-Fed and his ex-wife Britney Spears will be extending their current custody arrangement when her blockbuster striptease show new album tour crosses the Atlantic.

What that means is Federline will also be making the trek to Europe so that Spears can continue to be close to their sons Sean and Jayden, 3 and 2. No word on how much he will get paid for his time - but dude needs the cash!

"They worked out an arrangement to facilitate her being able to go on tour without having to sacrifice her ability to see the kids," Mark Vincent Kaplan says.

"She'll go on tour, she'll go to the venues, but Kevin will be there with the kids. There won't be any change in custody in Europe or anywhere she's on tour."

The once-estranged exes first hammered out a modified joint custody deal when Britney Spears embarked on her Circus tour in March 3 in New Orleans.

"Kevin is happy with how the kids are doing, and he's happy that he's been able to work out an arrangement where Britney is pursuing her professional goals, and Kevin is rooting for her every step of the way," Kaplan says.

He was also rumored to have nailed Britney backstage at one of the shows, to the dismay of current girlfriend Victoria Prince, but we'll chalk that one up as a rumor.

As for how Sean Preston and Jayden James Federline are handling the whole situation, "The kids are great, they're really happy," Kaplan stated. "They are both very well-adjusted kids, as well-adjusted as you can expect."

"They will always push the envelope, but I think that they have the absolute privilege of having two parents who absolutely love them. Everyone has worked for making sure that they're not a product of all of the attention and commotion."

As for Victoria Prince, Kaplan wouldn't confirm whether she'd be a member of the overseas entourage, but he says she, Sean and Jayden "have a good relationship."

The Circus Starring Britney Spears is off to London for eight gigs at O2 Arena, after which it's off to Dublin, Paris, Stockholm, etc., before ending July 26 in Berlin.