Turtle in Paradise by Jennifer L. Holm

When Turtle's mother finds employment as a housekeeper for somone who doesn't like kids, Turtle ends up going to her aunt's house in Key West.  Turtle meets her cousins, who run a baby-sitting enterprise who call themselves "The Diaper Gang."  Unfortunately, its a boys-only club, so Turtle isn't allowed to know their secret diaper-rash formula.  But when she discovers a secret map, will she share it with the gang?  Read Turtle in Paradise to find out!