I think you're missing my point, celeb. I imagine you're looking at this through our generation's eyes, where the woman was always expected to prep for and entertain guests, no matter who they were or which side of the family they were from. And the guy practically got a medal if he pitched in, LOL! The fact that you say, "my poor son did his best" underscores that for me. Why "poor?" Why isn't he expected to cook for you, etc., as much as his partner is? Even if it's true that she doesn't care that much for cooking and cleaning, that doesn't let him off the hook entirely.
I know, I know, you and I come from a different time. But they're more likely to be doing things according to how many young couples (not all, of course) do it today.
I may be wrong, of course. But IF I'm right, no worries - I'm NOT saying he sluffed off. I AM saying that he probably has a lot to learn about entertaining guests. And that he MIGHT have been hoping that his partner would cave and do more of the work, after all.
One thing I totally agree with you on is that it's rude not to be there when an invited guest arrives, unless, maybe you're late by accident. Some people, IMO, take this yours/mine thing too far (if that's what this was about).