What about this dichotomy? Is the emergent church holding on to the concept that “we are not of this world?” I think it’s terribly harming to teach children that they’re not supposed to belong, and then force them to operate in a society…

I agree with you. There has to be a real sense in which the people of God is ‘not of this world’ - if the church is meant to be a new humanity in Christ, that must constitute a real difference. But I would understand ‘not of this world’ to mean something like set apart for the sake of the world - it entails an orientation out of love towards the creation, not away from it. That ‘towards’ must mean that we allow ourselves and our children to manifest, without a sense of shame, the fulness of created life - working, playing, exploring, creating. There is no reason to think that the ‘new creation’ is less wonderful, less diverse, less exciting, less magical and mysterious, less deeply and pervasively relational, than the world that God originally made good.