Virginia -disposal Of Personal Property At My House

Location VA. 5 years ago my family made the mistake of helping someone out during a difficult time, and allowed them to temporarily store their personal property in our barn when they lost their house. We have been communicating with them for approximately 6 months requesting that they remove the property. We have no formal contract and were doing this for free. I've tried researching and found this might be a case of gratuitous bailment, but don't know how to legally move forward, as they don't want to deal with it on their own. We are trying to sell the house and this is holding up the sale. How do we properly move forward? Send certified letter that they have 30 days to remove the property then throw it away after that period passes? Using a throwaway account for privacy reasons. Any help would be greatly appreciated. Thanks