I also used OpenDNS.
I am not sure that it requires installing something on the router, maybe I do not remember.
You can do whitelisting – allowing only specific sites or groups of sites.
Also, whether it is for yourself or a kid – make sure there is a positive motivation in using electronics: learning, taking classes, and focus on expanding these positive activities. After you do work for 10 hours on a computer, you may want to do something else for relaxation.