With HP, I was much more upset about Sirius and Dumbledore than DS5 was! I was shocked at how well he handled the whole series, since he still sleeps with a light on and is my just-like-mommy scaredy cat. Book 7 gets REALLY scary, I thought, esp. with George dying, but it does make you feel a little bit better about Dumbledore, doesn't it?
With Santa, etc, I accidentally blew it about the Easter Bunny this year by buying stickers and candy for the family egg hunt in front of him. He acted like it was no big deal at the time, but was very sad for the entire day.
He recently lost his first two teeth, and even though I'm pretty sure his logical mind has figured out that her story has some problems, he's still into it. We've just made it fun by giving the tooth fairy a bit of a humorous cranky attitude in the letters that she leaves with the money. He's having a lot of fun with those.
I think DS also really wants to believe in Santa, so we're good for awhile. Since he knows all about St. Nicholas and we are also a reliigous family, I think he sees the parallels pretty clearly. Besides, don't we all still want to believe in the big guy? I remember being in college when my parents started making us lug our own presents from the basement to the tree after Midnight Mass. It was such a bummer to not see those presents magically appear on Christmas morning!!
