How to get rid of yellow jackets?

I have some aggressive yellow jackets that har my kids in their pool. I can't find their nest, but they fly at top speed into our faces, and I would leave them alone but I don't want my kids getting stung. Anything to keep them away would be great but something to kill them off would be fine to. Like I said live and let live and all but these guys are s and attack unprovoked.