The best way to get rid of the rats, and safest way for both your kids, dogs and the rats themselves, is to get rid of the reason they are there in the first place. Are there waste receptacles around? Open garbage cans and food? That is what attracts the rats to begin with. And like someone else mentioned, the dog poop can also keep the rats around, because they love to eat it.
I am not sure of any natural way to keep them out though (maybe google "humane and safe rat removal". I am sorry. I know there are humane traps that you can use to trap them and the release them FAR away, maybe in a forest preserve or field.
I am sorry you are having this problem. I actually like rats, I am an animal lover, but I do realize they pose a health hazard. I hope you find something that works.