The Moon by Night — Madeleine L'engle

As if simply being fourteen-years-old weren't bad enough--what with the usual teenage angst and uncertainty, Vicky Austin's always comforting and reliable home life is changing completely. Her brother John is going off to college in the fall. Maggy, an orphan taken in by the Austins two years ago, has gone to live with her legal guardian. And the rest of Vicky's family is moving from their quiet house in the country to the heart of New York City.
But before the big move, the entire Austin family is taking a meandering trip across the country in their station wagon, stopping to camp along the way, with no set schedule and not a single night of camping experience among them.
Wild animal attacks. Life-threatening natural disasters. Cute boys on the prowl. Anything can happen in the great outdoors.