Cameron Diaz, Justin Timberlake wedding details

"Cameron's worst nightmare is having her wedding splashed all over the press," says the source. "She's willing to forgo a big shindig to keep her big day private." Which means heading back to the couple's favorite sunny spot - and relatively paparazzi-free paradise - Hawaii.

. "Hawaii is their favorite, so they decided that's the place to do it," says the friend. "The plan is to invite a few close friends and family on a weeklong vacation, then have a casual sunset wedding. Then they'll stay another week to surf, relax and honeymoon."

"You'd think that Justin would be the holdout, but for the past year, he's been pushing for marriage," says the insider. "He's always been a one-woman guy; he's traditional that way."

(A rep for the actress denied the couple are engaged or have plans to wed.)