There might be a better article if you search deeper than I did to come up with a quick link, but here:
https://blog.heckel.xyz/2013/07/01/how-to-use-mitmproxy-to-r...
As you say, it's also iOS/Android only. No PC option for kids at all.
There are so many safe for any age videos that have a bunch of kids with the worst, most cynical attitudes and no respect for authority and then wholesome shows with "intense emotion" or whatever that get rated tv-14.
So I download everything and put it on a USB hard drive hooked to a media hub.
Edit: Looked into this myself just now. VLC Streamer looks decent, as does Infuse by Firecore.
You could drag an icon to the desktop for an HTML page with thumbnails if it was necessary to get fancy.
The Power of Block is powerful, and denial of it a major Internet dysfunction.
I do believe you can hack at Squid to intercept HTTPS and terminate if for you, as well as run filtering (Squidguard), also possibly Dansguardian. Though I've not fully researched this yet.
If it were possible to mitm HTTPS specifically for YouTube that would still be a lot of work, maybe a good Raspberry Pi project.
Alternatively, there is always kids.youtube.com which is weirdly just an app for Ios/Android. I haven't tried it, and myself have actively disabled/removed all Youtube from being accessible by the younglings. Curated media, decided by me is all they get to watch then.