I would recommend working with a trainer. I know you want everyone to be together (who wouldn't?) but I suggest keeping your dog separated from guests until a trainer can step in and assess the situation. Maybe your dog is being territorial of the new space? Or fearful because the space is smaller and he feels cornered when guests come in? Perhaps he is being protective of you. Or there could be something medical going on. It wouldn't hurt to bring him in for a vet checkup just in case.