I understand your point about using Dansguardian. However, you can also enable Google SafeSearch in the SquidGuard config file, I know for a fact as I have done it an K12LTSP deployment and just finished working with one of the developers of the SquidGuard package in pfSense (firewall/gateway). The reason I would like to use SquidGuard as opposed to Danguardian is that it is less resource intensive and performs much faster.
I would like to work with the developer/maintainer of the SquidGuard howto for SME Server to get it to be as robust as the one in pfSense. So if you are that person, lets make this happen.
Thank you,
Charlie