I recommend using OpenDNS - https://www.opendns.com/home-internet-security/ that provides site protection by categories and per domain. Additionally, there's ability to permit/allow specific domains if the domain is blocked by the category. It's pretty simple to setup by changing the name servers at router, or directly on each device. I've personally used for about 5 years.
Caveat - there's a limitation to know is encrypted VPNs can be used to bypass the filters, the kid's playground chatter gets around with methods to beat parental controls. Resolving blocking encrypted VPN takes more effort using a combination of hardware and software.
Good Luck!
