It was a really good idea - but what a depressing movie!
So John figures out that the code is for the event's date, number of deaths, and the exact location by longitude and latitude. He tracks down the old school teacher and Lucinda's daughter (and her daughter Abby), who at first doesn't believe him, until he predicts a major disaster. She says that her mother, who died, predicted a date that she would die also - October 19th.
Meanwhile, a huge solar flare is heading towards earth that could cause devastation, and is already blocking out electronics and communications.
As the world is going mad around him and people looting & fleeing their homes, John knows he doesn't have the finished piece, and breaks into the school to find the same old door from 50 years ago. He takes it back to his house and strips off the paint to reveal the rest of the numbers - which end with "EE" - for everyone else, the date that the rest of mankind will die. The coordinates are to Lucinda's old house, where he thinks they will be safe.
His son keeps seeing aliens/angels and himself has seen visions of the future. Also there are a load of black pebbles that keep appearing.
Diana is killed in a road traffic accident, but the whispering aliens rescue the children and they meet at the cabin. Down the road a little is a huge area, filled with those black pebbles.
A spaceship is waiting, and takes Caleb and Abby off into the sky. John returns to his own parent's house and there they wait bravely to be incinerated by the huge solar flare.
The world is destroyed.
The spaceship lands on a new world with idyllic green fields - the kids get out, holding some rabbits they rescued, and in the background are a number of other ships that have similarly rescued kids from other countries across the world, so they can start all over again.