It may be not safe to use a free keylogger. I prefer to use a commercial one like Micro keylogger here. http://www.parental-controls-software.net/micro-pc-keylogger-for-windows.htm
I would go on a commercial keylogger. Try All In One Keylogger. I use All In One Keylogger to keep an eye on my 3 kids and it does a great job. I started using it one year ago after checking almost all keyloggers on the market and i can tell you for sure that it it the best and the easiest to use and it is totally invisible. You can download All In One Keylogger from Relytec.com site. They give 7 days of free trial: http://www.relytec.com Hope that helps.
I would suggest you to go with comodo! If you want the full protection, rightclick on the Comodo shield --> settings --> select proactive security be carefull as you will lose your previous settings (previous allowed/blocked apps) alternatively go to defense+ --> advanced --> advanced settings (sorry I can't remember the correct name) --> select all options if everything is enabled, Comodo will protect you from keyloggers http://www.comodo.com/
This is good advice. It sounds like you want to spy on your kids instead of protecting them. Keyloggers are pretty invasive. Just teach them safe practices.
There are many keylogger programs but it is difficult to know the best keylogger software that works for the purpose.. what I know is http://www.spyrix.com/ is an invisible keylogger program, if you use it with any pc then it would be invisible to others, hence it works for the purpose.
If you need a parental control tool, you can search the Internet and find many. Some websites browsers or social networks have parental control functions. If you want to realize parental control on PC,I recommend you to try professional third party software which has functions of site block and time control,etc.I have used parental control program of anykeylogger(http://www.anykeylogger.com/keylogger.html),it works well,you can also find other fine programs on the Internet.
why would you want a keylogger? if you want to prevent your child from accessing bad website it is better to get web filter program or parental control program http://en.wikipedia.org/wiki/List_of_parental_control_software