Depending on the age, I really don't see the faith component as being all that difficult for kids. There's a huge portion of a child's development where they rely on their parents for information, and if a parent said it, it must be true. Isn't that just like faith in the divine? And if a parent says God exists, then their faith in their parents as authoritative sources of information gives becomes faith in God.
So, most of the questions come from trying to integrate that information with anything new, especially when there's an apparent contradiction. It's just like when a kid notices the rain hood over the chimney... they know Santa is fat, they know he comes down the chimney, and they know there's no way a man of any size is going to fit. The child does not question the existence of Santa, the child questions the method by which Santa is going to get past that hood.
The REALLY difficult questions usually begin to come much later, when the child learns the benefits of questioning received wisdom and gains familiarity with the scientific method.
