It sounds like you are trying to be reasonable about things. If the problem can be solved with words and some warnings from the Sheriff, then that's a good thing. You certainly don't want to set up a situation where that family wants to get even with you. i hope everything calms down and you...
i concur - file police report, put up game cam, and maybe get some bullet-proof vests! Clearly talking to them isn't going to work, unfortunately.
So, are these folks owners or renters? Because if they are renting, you can get the owner's name and address from the county assessor's office...