One can be interested in faiths and their evolution, and in the myths produced by various cultures - study them, even - without believing that a word of it is true. I'd love DD and DS to read about Greek, Egyptian and Norse myths when they are older, as well as Bible stories. It's daft to ignore them, given how ingrained they are into culture and history.
But there is a big difference between that and "believing", even if your belief is tinged with doubt. We don't seriously expect universities and scholars to study fairy-ology, or tealeaf-reading-ology, or the Celestial Teapot, or the effects of crystal healing. (Actually, depressingly, I bet someone, somewhere, has a grant to study crystal healing...) There is as much - or as little - evidence for these as there is for God. We are blinded into accepting theology as we are currently mired in Western Christian culture.
One thing Christians and atheists can agree on is that Christianity is a young religion, still growing , and still finding converts all over the world. 2000 years is nothing. This is interesting for Christians, because it means Christianity hasn't peaked yet and it can be used as evidence of its strength (millions of people believe it, therefore it must be true, right?). It's also interesting for atheists, because we can speculate how different things may be in 5000 years or so, when Christian monotheism is regarded with interest as a product of its time, just as the Egyptian and Greek polytheistic myths are today.