Every month, a slender, shrink-wrapped paperback book like "The Little Engine That Could," "K is for Kindness" or "Ice Cream Face" arrive in the mailboxes of parents with children under 5 years old.

Saving for a child’s future is an important part of every parent’s financial plan, but for many, the task can be daunting. According to a recent LendingTree study*, raising a child to adulthood costs ...