Make posts on this forum asking for other young players then send them friend requests on PSN. You can also join a Minecraft community on psn and post on the message board looking for people to play with.
You could post that either here in 'servers' or in 'looking for', just say that you are looking for a kid-friendly server. If you aren't getting any responses here, you could also try the PSMinecraft Subreddit, they usually have a few people looking for servers/friends for their children. Good luck dude