It can be a tricky situation, I agree!!
I think that, obviously in a school and certainly in the elementary setting, that it's so not okay to tell a kid what to believe, not believe, what's real, what isn't, etc...
I think that your egg story is brilliant with that! It's cute and fun, and shows that even though we have strong beliefs, we don't have to even necessarily share them, and we certainly aren't here to brain wash other people's children.
I manage homes for persons with disabilities. For the most part, I just don't talk about my own beliefs, but I support theirs in any way I can. There have been occasions where I did actually have to lie, in a round about way, in order to allow someone to have the belief that gave them comfort. I don't feel like I should be responsible for 'educating' vulnerable adults or children to either side, but I do make both sides known if someone asks.
One of my guys, when I started working, would say "Maybe I'm an ATHEIST!" when he wanted to shock or scare staff. When he did it to me, I just said, 'Yeah, well, a lot of people are!'. He looked at me with big eyes and said "Well, maybe I'm a SATANIST then!!!" I gave him the same answer, and he hasn't brought it up in that way ever again. lol.