How do I get rid of snakes from my yard? Repellents?

So far this summer, I have seen 3 snakes in our backyard. I have small children, so this is a huge concern for me. I am considering snake repellant...like, Sulfur...but I was wondering if repellents are effective and mainly....will it trap the snakes inside our yard? Like, if they are already there will they not leave once I put the sulfur out?? I would really appreciate any suggestions or help on this matter.