The extremely inconvenient adventures of Bronte Mettlestone

Bronte is ten years old when she receives a letter saying that her long-absent parents have been killed by pirates, and the lawyers tell her that their will (reinforced with serious magic) requires her to deliver gifts to her ten other aunts (not Aunt Isabelle, whom she lives with), and to start the trip immediately and alone--but as she travels the kingdoms, she begins to suspect that there is more to this journey than delivering treasures, and that her parents had more secrets than she ever realized.