Basically they were all dead. The family, the "ghosly" woman and the baby. The families car hit the woman with the baby, the impact killed them all (except the daughter of the family).
What we in the film is them in limbo, awaiting whatever the next life is. They're oblivious to the fact they've died however, and the car that drives past is a collection man of sorts, transporting the deceased from limbo into the afterlife.
As the others have said, the place they were heading to turns out to be the nurse's name, the one who recusitates the daughter. I assume the whole trying to get to the town of the same name, was the young woman's unconcious, and her trying to survive, and not die as the others did.
Not sure about why the nurse was approached by the collector at the end. I'm guessing this was just put in as a snappy ending, as opposed to having anything to do with the plot.
Overall, the film is just a metaphor for how people might cross over into death. In the film, they weren't aware they were dead, and it took a while for the daughter to figure out what exactly had happened and why everyone was being abducted