I don't use a keylogger exactly. Each family member has an a separate account under the XP machine. I use Norton Internet Security (as bloated as it is) and some of the filtering tools on it but under that layer I use...
SafeEyes (InternetSafety.com) which allows me to set up accounts that match every family member (or computer account) and allows me to control what websites can be visited, what types should be blocked (for the younger kids I can block everything but grant access to specific sites such as Disney, Lego, etc.) it allows me to control how many hours a day and what hours of the day the internet can be accessed by each account, logs what sites have been visited, what blocked sites have been attempted, if I choose, records Instant Message traffic, and will alert me (by email remotely if I want) if 1) banned sites are accessed or 2) personal information (home address phone number etc.) is transmitted. A single license can be installed on three computers and the administrator can control a machine that is remote from that location (eg. you can control your home computer from work).
Even this system isn't perfect but if gives us some comfort level with one teenager and two preteens in the house. When we've seen the boys playing violent games we didn't like, I accessed their log files, found what sites they'd been using and blocked them. Obviously, the kids aren't fond of this system but my wife and I have been pleased. There are a few features that I would like (particularly the ability to control local computer usage time instead of just internet access time) but this is the best we've found so far.
I'm sorry I have no idea if this will run on Ubuntu.
