I hate long journeys too, I usualy take my ipod (120gb so I can take all my 10k + tunes with me lol) and maybe a crossword/puzzle book. Unlike you probably I do enjoy spotting cars, animals in fields, truck drivers picking boogers etc :p
I worry a lot about the same things too, but I've come to the conclusion that I cannot stop living because something bad may happen to me. Think of all the GOOD things that might happen on this trip.
You must also talk to your family & let them know your this worried about it, sit them down & explain seriously. Your fears are real and they must listen. If your finding it hard to say it, write it down on a piece of paper or on your computer & have them read it. Keep it short & to the point.
I hope you have a good trip, staying away from home can be just as much fun as it can be worrying, I hated every last bit of the ride when we drove to the south of france a few years back, but once we got there it was amazing.