1) On the first day leave early in the morning like 4 AM. They usually do wake up around six because of the light outside, but for some reason those morning hours go by a lot quicker than later in the day hours.
2) Save the movies/video games for last. We have kind of an activities hierarchy where we have them read our do their own activity, then do some audiobooks and then movies gaming last.
3) A good audiobook can make the drive more enjoyable. We have liked: the Lion, the Witch and the Wardrobe, Number the Stars, Mr. Poppers Penguins, the Secret Garden, Matilda (or anything by Roald Dahl), Charlotte's Web, Sarah Plain and Tall, Little House on the Prairie, and Harry Potter of course. My kids also like the podcast Circle Round. It's geared toward little kids a bit more, but the stories are really well put together and hold the attention of all ages.
4) Limit the number of stops, I am one of those old school drivers, but if everyone gets out and buys something at the convenience store each time, it really makes seem a lot longer.