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
https://chrome.google.com/webstore/detail/webfilter-free-parental-c/epniipcfpbjliciholgdeipceecgcfmj
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