I know nothing about this except Google is my friend. Filmora seems to have a simple solution...
http://filmora.wondershare.com/video...blur-face.html
Apparently you can try it for free to see if it works for you. The output video will have a watermark though. Then you pay $30 for a year license if you like and the watermark goes away.
This is totally worth what you paid for it and my 30second google excursion. I've never tried the software nor editing video. So, you know, it's slightly better than worthless.
It does seem to me though that you'll have to do this yourself. Sending the video off to anyone to blur faces would mean, well, a whole lot of potential for problems... :-(