I second this one. I do a lot of work with Blue Coat appliances and software and they are for the most part solid. The commercial-grade version of the software is free, so you can test it out and see if it meets your requirments.
Blue Coat did a training session at my company for a week and touched on this software a bit, the statistics were pretty scary.
for kids ages 15-17 who use the internet, 70% have viewed pornography online, 23% often.
1 in 5 kids age 10-17 have received a sexual solicitation over the internet
and these stats were a few years back, so it's most likely higher now. I would definitely try to do anything possible to protect what your child views, that's about all you can do, the rest is up to them...