Penny gave great advice. I’d also like to add to consider reminding the person one time that your son is working through issues. If the person continues to provide disapproving looks or is not being supportive, then THEY can stay at the hotel if they’re coming to your house. They are not forced to stay at your home if anything bothers them that much that they can’t at least try to be supportive and put on a smile instead of disapproving looks!
When things get really bad and I have to say something, I might say in private, “I can tell by the look on your face that you seem stressed out/angry, etc. I am also struggling with some anxiety about this.” Then the two of you can come up with a hotel close by that the person can stay at if that would help! Sometimes I like to call out people on their dirty looks, and it works like a charm 😉