Ability to only allow specific multiplayer worlds

Currently, the XBox Family setting for multiplayer for Minecraft is an all or nothing setting. I would like the ability to allow only specific multiplayer worlds. I have a realms world set up for my child to play with specific friends. But the only way for me to allow them access to that specific realm is by enabling all multiplayer worlds. I do not want them to have access to other public multiplayer worlds. There is currently no way to allow access to particular worlds/realms without allowing access to all multiplayer worlds.