I see what you mean Minedpiederama (what's your non-festive screen name?) and before we had dcs I think I'd have said the same.
But... IMO children have this wonderful ability, which they gradually lose as they grow up, to enter into the spirit of make-believe fully whilst also being aware on a ratoinal level that it is make-believe (IYSWIM).
For example...my dd (the same one) loves having long and detailed conversations with a hand-puppet on the end of my hand (he's a dog called Hamish). I do the voice but she totally ignores my face and concentrates totaly on talking to Hamish and telling him things about her day (stuff she has just told me 5 mins ago). I think that's lovely!
Another one...she has excema and needs creaming reguarly, so to jolly things along I talk in a broad west country accent (as opposed to my boring old r.p.) and act in the role of a nurse who has popped in to cream her. And she talks to me as if I am a real nurse! As you can see we do a lot of imaginative role-play in our house . So it is this capacity for suspended rationality which I think is unique and quite beautiful in children.
I think it is good for dcs to develop their imagination and to be able to believe in the magical and the wonderful and for that reason I am happy for them to embrace fantasies which I know they will undoubtedly grow out of.
As a christian I believe that God isn't one of these make-believe games so that's why I want to try to keep it separate and talk abouti in different ways.
I think your response is a very adult one - dcs see the world differently, and in some ways are much more complex and intelligent than we adults are.