There is a great book available from Voice of the Martyrs called The Story of Saint Nicholas: More Than Reindeer and a Red Suit.
The following synopsis is taken from the Voice of the Martyrs website store:
Buried beneath the legends and tales of Santa Claus lies a story of a steadfast, godly man who refused to deny Christ—Nicholas of Myra, or Saint Nicholas. Throughout the centuries, many of his amazing stories have been told. However, few have heard about how he suffered for Jesus Christ.
Under the cruel Roman emperor Diocletian, Nicholas was thrown in prison for refusing to deny Jesus as God. Upon his release, he continued following in the footsteps of Christ through his unreserved giving and courage.
He later met further opposition, this time from the church. After Constantine took the throne and reportedly converted to Christianity, a false teaching began to invade the church. At a meeting of church leaders, Nicholas stood up for Christ and slapped the face of the man spreading the lies. For this, Nicholas could no longer be a leader in the church, but that didn’t stop him from going out of his way to share the love of Christ by helping children and others in need.
His story of courage and generosity in the face of persecution from the government and conflict within the church is for anyone. By any Christian definition, Nicholas was indeed a saint. Your children will be amazed to read of such bravery and tenacity of the man behind the legend of “Santa Claus.” May their faith, and yours, never be the same!
(Fully illustrated. Hardcover, 50 pages)