Sorry to hear you're having to deal with this nonsense Alphaghetti.
I would think twice about having your neighbour speak to him directly. It's a great idea to have her there as a witness but not actively involved. You can control your actions, but not those of others. It's lovely of her to offer to step in, but in a confrontation like this, it's better if she doesn't dive right in, just in case anyone loses their head. Take notes, document everything, yes....talk to the guy, a definite no. Who knows how much it might escalate. She should just remain on the sideline (on her property if possible) taking notes.
My two cents - just email them or leave a voicemail stating that you are within your rights not to refund the money as per your contract which they signed. Let them know that you will not be answering the door to her husband and if you feel at any time that you are being intimidated or threatened, you will call the police immediately. It sounds like they're good and mad - you certainly don't want to bring this sort of situation to your home and business.
I like the idea of contacting the police just to give them a heads up that there may be an issue later. You could also include this in your message to the family.
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