The couple boarded a plane from Kauai to Maui on Sunday, East Idaho News and Hawaii News Now reported. According to East Idaho News, Vallow and Daybell were living in a gated community, staying at resorts and biking around Kauai.
Vallow missed a court-ordered deadline in January to bring her children – Joshua "JJ" Vallow, 7, and Tylee Ryan, 17 – to Idaho authorities. The two kids have not been seen since Sept. 23 in Rexburg, and police said they were missing in December.
Vallow could face a contempt of court charge for missing the deadline. Though sought for questioning, neither she nor Daybell has been arrested or face charges tied to the children's disappearance.
Vallow and Daybell, who has written and published dozens of books on apocalyptic events and near-death experiences, married weeks after Daybell's wife of 30 years and mother of his five children died in October.
Tammy Daybell's death was initially believed to be from natural causes, but her remains were exhumed in December, and autopsy results are pending after police said her death "may be suspicious."
Vallow's ex-husband Joseph Ryan, the biological father of Tylee, died of an apparent heart attack in 2018; ex-husband Charles Vallow died from two gunshot wounds to the chest after Lori's brother Alex Cox shot him in July; and Cox died in December of an unknown cause.
Authorities have not said whether the cases are connected. Many details of the legal proceedings in the disappearance of Joshua and Tylee have been sealed.
After police announced Joshua and Tylee were missing, attorney Sean Bartholick issued a statement on the couple's behalf, calling Daybell "a loving husband" and Vallow "a devoted mother."
Though the circumstances may appear suspicious, prosecutors will wait until they have a solid case to file criminal charges, said Samuel Newton, an assistant professor of law at the University of Idaho who worked on the defense in the Elizabeth Smart case.
"I'm willing to bet what everyone is trying to do is get enough evidence to get an arrest and prove some sort of felony," Newton told USA TODAY.
Arresting Vallow on a contempt of court charge may not help prosecutors if they do not have a strong case, Newton said. Idaho would have to pay to extradite her from Hawaii.
"What they don't want to do is to file a charge and then have it get dismissed because there's nothing to support it," he said.
A potential crime in each death and disappearance surrounding the couple would have to be proved independent of each other, he said.
"The rules of evidence ... don't typically allow us to judge a person based on their past conduct. You're supposed to judge them on the facts of this case," Newton said.
Follow USA TODAY's Ryan Miller on Twitter @RyanW_Miller
This article originally appeared on USA TODAY: Lori Vallow: Missing Idaho kids' mom, Chad Daybell traveling in Hawaii