Oh, good god, stay away from the global feed. You can't moderate or filter the global feed in any way.
If you're wanting, or expecting the global feed to be moderated, that's not possible. That's where the censorship resistance expresses itself. There's no mechanism that can stop anyone from posting anything to the nostr global feed.
Your nostr client is designed to pull from the global feed things your interested in. Any and all moderation is done by you, using your client. That's the point. Your not getting just the things that someone else has decided to show you. That's more of a Mastodon thing.
Follow people and hashtags. Use a DVM. That's those, list generators that pull say, the most zapped posts for the last 24 hours.
As for your concerns about children accessing inappropriate shit on the Internet. Well, they're going to unless you stand beside them at all times and watch everything they do. There is no other way to stop them. Any company selling you anything that purports to keep children safe on the Internet, is lying.