Great idea, huge actually. Did you use claude code? It could help you integrate Stripe for billing, at least say "Free for now" and keep this in mind for later.
As a grandparent without your skills, I am impressed with the idea and how you included your son in the development. Especially useful for parents who (like you) wish to delay smartphone purchase for their kids. Is any of this patentable? Sell to a toy company for mass production?