Unorthodox tip: play into that. Like, actually start ranting about how they pretty much ruined timespace by doing that, then blow their minds with how the Universe we know will decohere and become a quantum soup! Then explain what all of that means and witness their minds exploding a second, third, and n-th time in front of your very eyes!

I'm not a parent, but I think the tendency to treat children as needing to be protected from "grown-up talk" - especially when it's playful (I mean, friggin' what?!), is a form of Otherisation.

My experience so far with the "say it, see what happens" philosophy I've adopted is that kids love this shit! It expands their horizons every time you present them with new information, even if it's dumb make-believe! Sure, they're more likely to start imitating behaviours, so we should be mindful to at least contextualise the more "out there" stuff, or filter it out until they gain the perspective necessary to process that stuff, but if one has a way of presenting it truthfully and thoughtfully, do it, I say!

The main thing I remember from childhood was how frustrating and confusing it was to see the grown-ups behave as though I didn't have a fucking clue as to what they meant or did, when I understood exactly what that shit meant. It punched my still-forming sense of self-esteem in the gut so hard, that it refused to participate anymore, y'know? It's like someone's constantly talking like you're not in the room, and it's alienating.