Two Cult, I'm really glad it worked out with you and your wife. I am aware of a number of less than successful stories about one partner disclosing non-belief to the other - several here on A|N. Congrats. Sounds like you handled it with more skill than a seasoned diplomat. Best to you and yours.
BIG sigh of relief!! Thanks for keeping us posted along the way.
Kids should be easy enough. Maybe start with the history of Christmas (taking over the pagan celebrations)then eventually move on to the questionable existance of Jesus as a historical (rather than supernatural) figure.
Just be matter-of-fact, if they're reaching the age of reason (whatever that may be- maybe around the same age they start doubting Santa Claus) they most likely have doubts of their own. Even my fundamentalist nephews have been saying stuff like "Jesus wasn't really born on Dec. 25th" and stuff like that.
In fact, they will be the ones who question the believers in their peer groups, and start to re-balance the scales of belief around them. This is important, as you know.
Your wife should be greatly relieved to learn that the events in and around her life have nothing to do with punishment or a need to feel guilty.