@D35J Hi, to actually answer your question instead of just giving an opinion on Avast itself:
It's really up to you. If you feel you need the extra features of the extension, like the site reputation rankings, then by all means use it. Just be aware that extensions sometimes cause issues with web-sites that are not always easy to figure out for the user.
Note that Vivaldi's tracker blocker is for privacy, not security, even if the ad-blocker lists will block requests to some known malicious sites.
If running Avast locally it should also block access and warn when attempting to access a malicious site. And I assume the lists it uses are updated more regularly than the public lists used by Vivaldi.
So my opinion is you don't need the extension itself, unless you need the site reputation ranking feature. But keep Avast running locally for overall system security.
To be honest if your kids are over 10-11 yo, you should let them and maybe force them to watch those kind of stuff, is better to show them and explain it, than letting them finding themselves, also they can always use incognito mode or use the mobile versions to bypass a dns filter U,U
Maybe this can work :'v
if not changing the filters inside the OS, or if you feel that you know what you are doing, you can go directly into your router/modem configuration and apply the settings there, so it wouldn't matter if it's a phone, a laptop a desktop or a smart tv, you wont be able to enter to watch your favorite videos on pornhub c: