I would say the most important thing to teach them in this arena is to think for themselves. If they come to the conclusion that Christianity is true, then fine. Same with Islam, Sikhism, Paganism, Atheism etc.
When I have kids, I just hope that whatever they believe is what they've concluded makes sense, not what Daddy/a teacher/some guy on TV said was unquestionable truth.
On a slightly related note, I've been thinking about the oft referenced "Extraordinary claims require extraordinary evidence" thing. Atheists tend to wheel it out with the idea that God is obviously the extraordinary claim and that this instantly puts theists on the back foot but in this sense it's pretty much begging the question. If your whole life has been filled with "look what God did, isn't He amazing", then the extraordinary claim is obviously that there is no Creator and that the complexity we see around us arose naturally. Logically, "God is silly, show me some proof" is on the same level as "The creation is proof of a creator"
or She, for the benefit of @accalia