Uh...fly.
Unless you really love your kids
That's a joke. I love the romantic sort of idea of driving across the country to California..but then I start to think about the fact that I would have to drive back. Seriously..hit up kayak.com and book the cheapest flight. By the time you factor in gas, ALL those meals, hotel stays, a car check up before you leave ,possible flat tires, a new transmission
they'll add up to about the same.