Their kid, your dog, your property...Ohio has a dog bite statute.
Ohio's Dog Bite statutes basically states that if your dog causes any injury, death, or loss to person or property that you are liable. It is found in Ohio Revised Code 955.28.
One exception to the liability rule states that you are not liable if an individual was teasing, tormenting, or abusing your dog on your property.
"Teasing” basically means to annoy or to trouble or to worry persistently, to be troublesome, or to pester whereas "tormenting" is something more and implies some torture or pain. And, "abusing" is mistreatment which includes some physical injury or pain to the animal. Olmstead v. Forsthoefel, 2013-Ohio-220.
In the Olmstead case a 9-year old boy having a bad day admitted to pulling on the ears of a four-year old Labrador-terrier mix. He acknowledged that he knew he should not pull a dog's ears. The dog apparently was not pleased and bit him in the face. Mom and boy sued and lost.
On appeal, the Court decided that the boy (while on the dog owner's property) had pulled the dog's ears hard enough to annoy the animal and elicit a reaction.
(Just a closeup dog picture...not the dog in the story)