Not quite the correct application but linkwarden would work. Stores all your links but also backs everything up via html, plain text, and pdf. You can categorize content and tag content. Then there are filter and search tools.
You can just give it PDFs and it will import them over as well. Only saves them as a pdf but still would work.
I’m guessing this is not the best approach but wanted to give you options.
How difficult it is has a lot of variance. Unifi make it easy to get up and going for example.
Unifi Network, make network, content filtering: family, save. Make WiFi, assign to network, save. Then you can just never give you kids access to the default network. Or you can blacklist their devices. If you want to get more advanced firewall rules are fairly easy to add as well.