There is a great book out there that maybe you could tell the parents about. It explains the story behind St. Nicholas and the truth with that story. It's a great Christian story for kids.
It's called...
Santa are You For Real?
http://www.amazon.com/Santa-Are-You-...2710402&sr=8-1
I don't know why it's so expensive on amazon (I paid $12 a few years ago) but you can read some of the reviews here about it.
So it doesn't take away all the magic and puts a little bit of truth behind the concept.