In regards to all the posters who say my wife and I need to be on the same page, I agree, and I believe we actually are on the same page. She doesn't want dogs here anymore than I do. She feels that over the past year or so, her children have been displaying a lack of courtesy towards us, and to her in particular, in that they hear what we want, but do whatever they feel like and then justify why they did it.
Should my wife have been more direct with her son? Yes she should have. I have always said that the one person she could always count on to stand beside her and be there when she needed someone was her son, so this may have taken her a bit by surprise. I think she expected him to say ok, I'll find other accommodations for the dog when she told him I was less than thrilled with his idea of bringing the dog to our house.
I told her I was going to call him and tell him that he misunderstood his mother, that it was not a matter of there were issues that needed to be addressed if he was going to bring his dog here, but rather the answer to his question was NO!, your dog or any dog for that matter, is not welcome at our house.
She asked me not to do that, she would rather talk to him face to face. She did promise she would tell him that this is a one time event, and that from now on, when they come to visit, he will have to either find someone to watch his dog, or put in him a kennel.
For those who have suggested a pet friendly hotel, the biggest drawback to this is that he is not bringing the dog because he loves her so much he can't bear to leave. He is bringing her because he is too cheap to shell out 100 bucks to kennel her for the weekend. A hotel room would cost him a lot more than 100.00 dollars for a two night stay.