I couldn't find any good firmware so I went low tech. I bought an access point and a programmable timer.
Just set the AP up with different WEP key and programmed the timer to power it up when we want the kids to have net access. As a bonus, my wife can walk into the master closet, push a button on the timer and shut down Netflix, FB, all of that.
Experience is what you always have about 15 minuets after you needed it.