I've long entertained a dubious regard for the practice of lying to children about the existence of Santa Claus. Parents might claim that it serves to make children's lives more magical and exciting, but as a general rule, children are adequately equipped to create fantasies of their own without their parents' intervention. The two reasons I suspect rest at the bottom line are adherence to tradition, and finding it cute to see one's children believing ridiculous things.
Personally, I considered this to be a rather indecent way to treat one's own children, and have sometimes wondered whether a large proportion of conspiracy theorists owe their origins to the realization that practically all the adults in the country really are conspiring to deceive children for no tangible benefit. However, since I began frequenting this site, I've been exposed to the alternate viewpoint that this realization may be good for developing rationalists, because it provides children with the experience of discovering that they hold beliefs which are wrong and absurd, and that they must reject them.
So, how did the Santa deception affect you personally? How do you think your life might have been different without it? If your parents didn't do it to you, what are your impressions on the experience of not being lied to when most other children are?
Also, I promise to upvote anyone who links to an easy to register for community of conspiracy theorists where they would not be averse to being asked the same question.
Well, yes: encourage them to develop social bonds to a group of secularists among whom altruist and/or idealist activities are highly valued, preferably one with mechanisms to prevent cheap methods for signaling altruism and/or idealism to displace those activities.
Of course, that raises the question of how to identify such a group... or create it in the first place.
Among secularists, the term ‘humanist’ is a good sign. I belong to a community of secular humanists (although it doesn't have enough families to help with raising children yet).
You can get a close copy of mainline Protestant church socialisation at a Unitarian Universalist congregation in the United States. (Individual congregations vary widely, however, and not all are really secular, with various degrees of monotheism, neopaganism, and pantheism all possible in the culture, although they should be accepting of anybody.)