Disregarding the voice and video requirements, a private Minecraft server or Realm is a pretty decent space for kids to hang out and let their creativity run wild.

10 or so years ago when Minecraft was coming out of beta, I was a precocious enough child to run a server on some spare hardware lying around the house. (Realms wasn't a thing until like 2014)

Good times were had between my friends and I, but that all changed after I started becoming intoxicated by the power. Whoops.

Give it a try, but I advise against giving a literal child the ability to ban people. I would know.