Youtube kids is designed for toddlers, and should probably be shut down entirely. What I'm talking about is something designed for 14 year olds where they can still subscribe to channels, have paid ad free, parental controls, etc. But not upload videos or use it in a social media way.

Youtube (regular one) is already designed to be kids-friendly. There are no war images since recent AI moderation rollout. There are a lot of very forbidden words which can lead to ban account. There are a lot of mildly forbidden words which just do not appear in subtitle. You can not say anything bully on comments - it will be removed instantly. I don't consider anything bad in YT except of the whole top of popular bloggers - because they are clearly aimed at low-IQ people. Just don't be a stupid, and your kids will not watch the bloggers. Buy more instruments of all kinds for your kids and they will watch a lot of educational videos explaining different know-hows.