Nice work on offline.kids and kudos for tackling screen-free play. I've been playing in a similar space. If you want something complementary for the inevitable “but why?” moments, you might like StudyTurtle Ask (https://studyturtle.com/ask). It’s a free, no-signup AI Q&A tuned for 3–9 year-olds with:

Strict age calibration (matching phrasing and examples to each developmental level)

Concrete analogies (“volcanoes are like shaken soda bottles”) and kitchen-table experiments you can actually do