I know this probably won't be much help, but are you kicking them off because of the download speed? I just bought a new router that's exteamly fast compared to my old one. I had a Netgear N-300 speed and it would top out about 1.7 mps download speed. If somebody was streaming a movie it would kill the speed. I bought a Netgear duel band N-600 speed router and it's downloading around 14 mps.
I don't know much about computers, but if they're streaming movies. You might want to look at getting a new router. Sorry I can't help on the lock out feature.