Is there any way that I can make the Shield require a PIN to do anything, like a lock screen?
Need to prevent kids from using it at all hours.
(Short of hiding the remote!)
I saw the 'restricted user' option but that just seems to lock out certain apps.
Might have to resort to an outlet timer to cut power. This device is intended for the living room with always-on availability for everyone in the household. It's not really designed to be a private device.
Are your children under 13? If so you might try Google family link. I use it for phones and tablets for my kids but haven't tried to tv yet. Their faq says Android 7.0 is the minimum requirement.
Your TV might have an option by itself
I keep the remotes under lock and key and the kids get them when I say. I also use the internet restricting option on my router to keep them off the internet certain times of the day.
If your router supports it, why not just set up a schedule to cut internet to it between certain hours. Without internet, a majority of Shield apps would be useless.