Here are just some thoughts from the few trips we have taken with Alex.
1. Get some new toys/books. I usually buy at least two new things. (One for the trip there, and one for the trip back) A new toy/book usually gives you some time.
2. Portable DVD player - it's a MUST!!!

Alex loves watching his videos in the car.
3. Snacks, snacks and snacks. We always pack lots to munch on and a cooler for the cold stuff. This is good both for the car and for when you reach your destination. It was nice to be able to give Alex fruit/snacks when he wanted them without having to go out and find food.
4. Be prepared to stop - and a lot. You may get lucky, but make sure you add time to your trip.
5. If you can time your diving for naptime, it will help. For example, it's about a 6 hour drive to my parents house. We usually leave after work, drive for about a hour and a half, stop for dinner, get Alex in his pj's, let him watch one of his videos and then he's ready for bed. He then sleeps the rest of the way.
6. Has your DD slept in a pack n play at all? We usually take ours with us and Alex has done fine. If not, you may want to see about taking naps in the pnp before your trip so that she gets used to it.
7. If you have room, bring lots of toys from home. Alex always like having things that were familiar to him on our trips.
8. BE FLEXIBLE!!! You may have great plans for your vacation (where you are going to eat, and do, and at what time). Those plans may go out the window if your daughter has any sleep issues. It can be stressful for the little ones to have their routine changed. Just be prepared to throw the plans out the window.
Have a GREAT trip!!
Kim