I'd guess you are a geek and may actually have a network already setup in your house. Grab an old computer (Dumpster diving, go through your own stuff and put one together or goodwill) and install IPCop. Then install URL Filter which uses squid. The added benefit of having a secure firewall that blocks, porn, ads, trackers, spyware and just about anything else you could imagine.
I currently use this system in my own house and at my current job. It's not perfect. Any person who REALLY wants to get at something can. It does however cause a lot less problems.
Side Note: Am I the only one who searches for motherboard models and the first site listed by Google has Adult Friend Finder adds? That's enough for me to install that software.