The lock for safe search on google does not work anymore because the website frequently redirects to the HTTPS version. The filter does not work, specially for images. It was mentioned a few months ago that this is only the case when you are logged in to google or something. Well, not anymore, I have no google accounts.
I think if you can't solve this, you should at least have a specific and efficinet option that does not allow google. Bing doesn't have this problem.