I am in a similar situation. I was raised Baptist, but am now agnostic with deep respect for (though not strict belief in) Buddhism. I do my best to respect all religions, and try to convey that respect to my children, but they don't have any doubt as to what I believe.

When opportunities present themselves, I do my best to explain what other religions believe and what it might mean to those people while trying not to interject my own opinion of the topic too much.

My kids know with absolute certainty that I do not expect them to believe as I do, and I will not be disappointed or resentful if they choose another path. Religion/spirituality should be a deeply personal and private issue and is absolutely nobody else's business.