PS - I make that point about Grants Pass, because I feel as though they wouldn't have taken their tragic turn if they *had* gone on in to Grants Pass - into a "town" - where they might've stopped, maybe even gotten gas or primarily, just some coffee for the journey - and *someone* would've talked to them about where they were headed.
There are gas stations on the Merlin exit although they may have been closed at the time the Kims were there.