Before we left on our East Coast adventure, we purchased a power inverter for the car. While KJ didn't really understand what the benefits would be, Chunk praised the use of one of these. As it turns out, Chunk was right. Power inverters are a lifesaver. You can not only charge things in the car using the regular car chargers, but the power inverter also has a regular plug on it. This was especially helpful in keeping Chunk's iPhone up and running.
We bought the Black & Decker 200w power inverter (shout out to KJs dad's company!). It works pretty well, and while not aesthetically that appealing it's definitely a useful gadget. So if you're going on a long trip, get one of these things. You'll thank us later!