We let our daughter "see Santa" last year.  I went upstairs to say goodnight "heard a noise" and went to look.  Dad was downstairs in the schools Santa suit and the top of the stairs has a view to the livingroom.  We watched him go from the tree to the fireplace where the stockings were and then dissapear.    My son knew what we were doing but my daughters heart was beating so fast and her adrenaline was going so much that she almost threw up over the experience.   :)  

This year we had to tell her the truth.  :(

...... Kendra