Easiest way to block device access to a web site?

One of my children, adult but special-needs, can't be trusted with his Facebook account. I'm otherwise comfortable with his using his computer, but would like to block his access to Facebook. Not just by changing the password and not saving it, but completely blocking his online access to even the login page.

From what I read, the best options are:

1. Blocking via router - but won't work for me; my S@gemcom 5260 can only block websites for all devices or none
2. Setting up a "child" user account with parental controls - not really optimal here; his account on his computer is fine as is, and unless I can just make it a "child" account, to put on parental controls, without setting up a new account, I don't want this route
3. Edit the hosts file - I've done this before, years ago, and it worked fine. Not too elegant, but works

Based on what I say here, are there other easy options for me?

I would edit the hosts file. Very simple and it works.

play2mefish said:

I would edit the hosts file. Very simple and it works.

Yes, and thanks. Upon seconds of reflection after posting, I realized this was the obvious best solution, and - problem solved. I think the last time I did this, it was with a resource-challenged computer running Windows 2000, and even the edit was a challenge, and then the much-larger hosts file noticeably bogged down browser performance. Not at all the case any more.