Can I put a pin or password on the channels from being added/ removed by my kids? They keep adding channels I don't want them having access to.
Yes, go to your account and update your pin preferences. Click on Require a PIN to make purchases and add channels. Then save. That should do it.
A PIN can block adding a channel, but there's no method of blocking someone from removing a channel. And removing a channel from one device will remove it from all devices linked to the same Roku user account. I believe that is something Roku should address, as it's been an issue for years.