Go with the plan to take their stuff to storage out of state. When they come back to get it, tell them someone broke in and stole it. You figured it was THEM that took it. If they want to tell the cops, let them. The cops will just give them the "civil matter" speech like before. They are out all of their stuff, cops won't do anything about it, and they no longer have a reason to keep coming back. It would cost money for the haul and storage, though.
Then let some hard, lead pipe-hittin' mutherf*ckers stay there for several weeks, lest they show up on the property again, they would be met with a warm reception. Then get some punks to stick potatoes up the tail pipes of these peoples cars, or sugar their gastanks, so the damage caused will be unrepairable. Or plant some crack into some of their belongings, call the cops, and tell them what you found. Or be there when they come onto the property again, chase them off, then have someone beat on you for awhile, call the cops, accuse them of the beating, and press charges.
I don't know how any of this would get the 10K out of them , though.