There is actually a religion, a merge between Christianity and paganism. Theres books and websites with information. Loom up Christopaganism (shocking name right? Lol)
So does Christianity...
How devout are you and the father? Because if you think about the values of both religions, they go hand in hand. Paganism (I believe, and I don't mean to offend if I'm wrong) is about loving, respecting and worshipping nature while Christianity is about the teachings of Christ which is to love and respect other people.
You can celebrate holidays from both religions and even attend services for both. It'll be compromise, but that is a good lesson in itself. And as your child grows, they can ask more questions and make more religious decisions for themselves. As long as your and your husband respect each others beliefs and show respect for each others beliefs, values and traditions I don't see how that would be confusing to a child.
And you can go to the library and look in the child psychology and religion sections to find a book about this.