Rather than attempting to cover the history and meaning of Reformation Day for you, I have enlisted those much wiser, and much smarter than myself to help with this. Below is a smattering of goodies (historical essays, theological blogs, music, and free resources).
The Glory of the Reformation by Kevin DeYoung. The theological, and practical significance of the recovery of the Gospel of grace.
The Ballad of Martin Luther by Marc Hays, this is a song concerning the life of Martin Luther. Enjoy.
The Reformation: Trick or Treat? by David Mathis. Make sure you scroll to the bottom of the page for some free resources.
‘Sola Scriptura’ Radicalized and Abandoned by Matthew Barrett on the importance of sola scriptura and the proper use of tradition.
Zondervan has also put out some books from “Reformed” authors on sale that could (should?) interest you.
If you are concerned about Halloween, my advice is to be wise, don’t play for the other team (don’t dress as the devil or a ghoul), be modest (no sexually alluring costumes), and be wise (yep, I said it twice). For something on the humorous side, read David Murray’s Five Christian Theologies Scarier than Halloween, and please note the sardonic tone of Dr. Murray.