I'd imagine most vegi's would think IABVU?
DH's family are with us for Christmas. They'll be 11 of us to cook for and BIL with obviously need something to replace the Turkey, no problem.
He'll also need separate gravy, hardly any bother.
I usually make a couple of stuffings and make sure one is meat free, again, no bother.
He also likes to have some vegi sausages to replace the pigs in blankets.
I like to do a good job with xmas dinner and I love doing the spuds in goose fat.
I ponder over this every time we have them for xmas. It's a PITA having to pretty much cook a separate vegi dinner alongside a traditional one, find space in the oven and get all the timings right.
Would it really hurt, for one day, if he was unknowingly more flexible?
The rest of the year when we see them, I just make something vegi for all of us, but this is xmas dinner and I like going to town a bit.
So;
a. Would he notice?
b. Would it be really, really bad?