Hot spiked apple cider?

im having a christmas party friday night. I want to serve hot apple cider piked. I want to keep it warm in a crock pot so that way people can continuosly serve themselves warm cider throughout the night. Also it need to be easily replenished. Can I just dump some premade apple cider into a crock pot on the "warm: setting and add some cinnamon nutmeg and liquor? and which liquor is best for this? An apple flavored liquor or something darker?