A hearty thanks to all for your thoughts and experiences.

It confirms what I suspected. Now I can't imagine a bride and groom being outdone by anyone (except maybe Ronald MacDonald! LOL) but somehow that doesn't relieve me of the obligation of being a worthy guest. My son is 5 and is really looking forward to wearing his kilt when it comes, but that doesn't have to be at this wedding. I may yet ask the bride (who is, I agree, the authority) but I think I have pretty much tipped toward blending in in a suit.

I'll update with the final result after the wedding for anyone who might wish to find out how the story ends. And I may yet post a picture of what I would have worn had I gone kilted. That kind of inverts the rule about pictures being the proof of events really happening. In my case my picture will be proof that the event didn't happen [in a kilt]?!

Again, thank you everyone!