What happens if we aren't covered under our HOwners ins.?

My son's friend broke his arm while with friends on our Mule(rec. vehicle) with another boy driving. While our main concern is for his friend to fully recover, we can't help but feel the stress of what happens now since receiving letters from the the injured parties ins. co. The injured parties ins. co. is going after our ins. co. and now the driver's (another boy) to be compensated for the $$$ paid out for medical bills. The boy is still not recovered and still in the process of treatment. We've heard from our ins. co. that we have no coverage because the accident occurred NOT on our property...and the mule isn't covered. The driver's ins. co. says the driver does have coverage. So now what? The injured party says they are not sueing us, they tell us this is just their ins. co. So... now that we know we have no coverage, will their ins. co. come after us personally... or will they get reimbursed through the drivers ins.? My son was not in the vehicle when it happened. He was in a different area. Their was no alcohol or drugs related, just kids out having fun and driving too fast while taking a sharp turn on a sandy sloped area. How long can this process take? And will their be a point where we need a lawyer?