Filters
Use OpenDNS, it's free to use. Also if you don't want to customise things you can just use their "Family Shield" set up and you don't have to sign up to use it (not shown on that page but is possible after clicking the "sign up" button 
).
).
+1 for OpenDNS Parental Controls for web browsing 
You should review your "Search Settings" in Google search to an appropriate level of filter.
If you were really keen, you could install a content filter in or after your router, such as DansGuardian
You should review your "Search Settings" in Google search to an appropriate level of filter.
If you were really keen, you could install a content filter in or after your router, such as DansGuardian