Can you talk about dinner plans in front of people who aren't invited?
My wife and I try to have people over for dinner once a month or so, and tonight, we're having three people over - Sally, and John and Jean. Every Wednesday, our circle of friends goes out for drinks, and last night it was my wife and I, Sally, and Paul and Pauline. We're all close friends, and I've had all of them over to my house for both small dinners and big holiday events. At the end of last night, I mentioned that we're having Sally over for dinner tonight, and Paul said to Pauline, "We're leaving," and got up and walked out of the restaurant. I should mention that Paul isn't a particularly sensitive guy, but he does enjoy creating an uncomfortable situation for a laugh. That's how our group of friends interacts. And it was funny.
My wife and Sally say that I shouldn't have said anything about it in front of people who weren't invited - even though they agreed that Paul was obviously going for a laugh, they think he was also a little bit offended. I can understand that if I'm inviting *nearly everyone* from our circle of 20 or so close friends that non-invitees would feel excluded, but it's a small gathering. I can understand if I spent the whole evening discussing plans, but it was one statement at the end of the evening. I don't think I've actually caused offense, or that something like this would be expected to cause offense.
Complicating matters is the fact that Paul is pretty well off, and has a large house that is well-equipped for entertaining, and I'm generally always invited to his events. On the other hand, if we're having dinner for more than 6 (including my wife and I), someone is going to be eating on the couch. When I've had larger holiday parties, I set up tables in the yard. I usually borrow them from Paul, actually. (November and December are a little more comfortable for eating outdoors than August here in Florida.) Speaking of the holiday parties, I'm infamous for creating a spreadsheet to randomly pick people to invite - even my yard is too small to accomodate all of our good friends, and I specifically didn't want people to feel left out. (I'm also kind of a nerd, and random number generators and complicated algorithms are kind of my thing.)
So - what's the etiquette for discussing a dinner invitation in front of people who aren't invited?