Drift House: The First Voyage

From the jacket:

When Susan and her brothers Charles and Murray are sent to live with their Uncle Farley, they instantly sense something peculiar about their new home. Drift House looks like a ship washed crookedly ashore. And when the children wake the first morning to discover that the house has floated out to sea, they find themselves immersed in a story that reaches from the watery depths to heights only a flying carpet can reach.

As Drift House sets its own course, and mermaids, pirates, and three mysterious keys lure them farther onto the Sea of Time, Susan must determine whether to rescue her brothers or to save the movement of time itself.

Filled with plot twists, magical creatures, and the language of classic adventure stories, this is a remarkable tale of three children who are given all the time in the world—but not a moment to spare!—to fulfill an extraordinary quest.