How to stop cyber-bullying?

My husband is always busy for his company, and he has little time to take care of our boys. MY felt unable to protect them in full-scales sometimes, moreover, I've been suspecting lately that my kids have been bullying online. I installed a NetNanny-type blocker on the computer, but it seemed not useful. I'd like to download a free keylogger to see what's going on, then I can take steps to stop it. Please, I will appreciate it if you can think of any free keylogger download. By the way, doesn't someone have the experience of stopping bullying?