I would agree if it were another time of year, but who in the world runs away or takes a "vacation" at Christmas-- with a nine-year-old? That makes no sense.There's probably more than one reason for buying time but I've always thought the reason for a week in particular was to give the impression that they would be back in time to go to school. This would make it more believable and maybe relieve some of the qualms the parents would have.
At that point, those parents would've signed up for a trip to Mars, if they thought they'd see their kids again.Well they were all standing at a bus stop a week later so what does that tell us?
The letter worked.