We had a version of this in our house from the other side. I consider myself pretty agnostic/universalist, although we're definitely a "culturally Chistian" household, singing Christmas carols, celebrating Easter and Christmas, decorations in our house include a selection of nativity scenes from around this world. He's been to church with my mom a few times.
I have exposed my son since he was very young to stories from world religions, and I've always presented it as "this is something some people believe is a true story, and some people believe is made up, you can make your own mind", whether it's a story about the Hindu god Ganesh or Noah's Ark. I think he does believe more than I do, the other day I asked him if he believed in Jesus and he shrugged and said "Yeah".
Anyway, my childhood bible was always on his book shelf, I think my mom read him a few stories from it (not in an evangelistic way, just here's a nice bedtime story), and I think I read him a few. He also went through a phase where he liked vegitales and I let him watch them, always with the knowledges that some people believed they were true, but not neccessarily me. One day he had a playdate over, in about Kindergarten, I found he and a friend curled up in a corner "reading" the picture bible together with my son saying "Yes, this really happened" and the other child saying "Nuh Uh, it's just a story", and telling the story of Jonah and the whale in a very 'creative' fashion. The other child comes from a family where one parent was raised Christian and the other Jewish but they don't practice much of either.
I reminded my son that different people could believe different things and that his friend didn't need to believe the stories were true, and called the mom who was fine with it. Of course I've also had to call this mom to let her know that our kids were making jewelry out of clean tampons, and she was fine with that too -- she's a pretty laid back mom.