In our families we rely on the K9 Internet filter.
It is a filter which is easy to set up and fine tune to specific needs. The best part - it is free. By tuning it ourselves, we can filter out what we don't want to see, and we are not subjected to censoring which is part of other filters.
After the filter is set up and tuned, under the wife/mother supervision, the wife/mother chooses a password and does not tell anyone what it is. This way it is impossible to "cheat" on the filter.
If a certain kosher site happens to be blocked, the wife/mother enters her password, the site is added to the kosher list or the filtering parameters get corrected. Then, the filter gets locked again.