I’ve been using SafeEyes at home for 3+ years on our Mac PowerBook. SafeEyes provides very good parental filtering and is one of the few clients available for OS X, but … the whole time it has been plagued with periodic crashes. In the middle of doing something, it just quits and nothing on the Internet works until the system is rebooted. After trying upgrades, uninstall/reinstall, the whole works, I give up.
I’ve switched for now to OpenDNS, a free DNS-based solution. What is DNS? It’s the Internet service that turns friendly names like “nytimes.com” into a 32 (or 128) bit numeric address. What OpenDNS does — if you enable the parental controls — is intercept those requests when they are for sites you’re blocking. It can do this with no client software needed. Just point your network setup to their servers, create a free account and configure your settings, and you’re good to go.
Unless your kids have administrator privileges to change your network settings (in which case you would need something very root, like SafeEyes, to stop them), this should work pretty well. So far it looks great. And did I mention that it’s free? You can choose whether to protect just one computer (as I did) by changing its settings, or point your router to it to protect everything on your network all at once. And dynamic IP/DHCP addresses are no problem: it has a light client app for OSX and Windows that will update your IP address automatically. Just be sure to set it to run automatically (read the “readme” file).
You might ask: why not use OSX parental controls? Because I don’t use Safari, and it doesn’t work with Firefox. I wanted something that is as light as possible on the client, as up to date as possible, and works for everything.