I almost covered this case because I knew someone would (reasonably) ask, but didn't for length.

I checked everyone's dietary restrictions beforehand. I served fake meat without informing them at my wife's request, because she knew her father (who is stubborn southerner) and brother (who is mentally handicapped) would both refuse to like it immediately. (A visit to an all-vegetarian restaurant would later prove her correct).

In all other circumstances where I've served fake meat to others it's been very openly labeled and/or pointed out.

I'm inclined to agree with everything you've said, but Thanksgiving with the in-laws is a special moral situation, vegetarian or not :)