Certain accounts always post reasonably kid friendly stuff. Like nostr:npub1sur5gd3mrfvcd4nh8dtsdh0ztrqrnaknff0lcfcfz5pn56n8eqkqv9sm0l and nostr:npub1tlgqfynfdyup4s4m8ge8yqpkm8ukxtfflv3dcxl4mra3e83x27vqrlj5tp

If there were many more who were trustworthy it might be possible to let a kid have access to a nearly normal Nostr client, but with the only difference being password-protected search and following.

Then you just subscribe your kid to whatever accounts you want them to see only.

Having much better filtering of notes based on keyword, not just hashtag, would also be a great idea.

Just a brainstorm.