Hi @adecooper
Thank you for making this post regarding the YouTube App, I'm sorry to hear your 8 year old managed to change the settings and watch inappropriate content. That is not ideal at all 😞
If you have a V6, then YouTube can be locked and only accessible through entering your PIN. Simply go to Help & Settings, Parental Controls, Lock Apps & Games and then select YouTube.
As @newapollo mentioned, the same function is also available on TV360 should you upgrade.
Hope this helps!
Kind regards,
Serena