About the spirit of giving and St. Nicholas you mean?
That's pretty good use of transferrence! Of course Santa is not a necessary component of the "spirit of giving". Nicholas of Nicea was nothing to admire, so your mention of St. Nicholas does get closer to the point. But the real point is that I want my boy to be a Christian, so the last thing I want to do is sit him down and explain, "Remember the nice invisble man who watches over you and gives you things? Well, really he's just made up."
When our child was five, she knew all about St. Nicholas and the three dowries and giving in secret without asking for reward.
But we never told her about Santa Claus. He's always been "silly", to use her word.