I abhor the idea of things made “for kids”. I learned to program when I was 10 on a Commodore 64. And we would wear an onion on our belt which was the style at the time… Sorry, where was I?
I’d just install a normal distro. Let the kiddo break shit and learn to fix it. Keep backups for recovery and probably isolate the system on your network for if/when kiddo does something stupid. Talk about security, being responsible, etc. We learn through mistakes not by playing in safe walled-gardens.