I noticed that the Odyssey hotel booking form has a section for special dietary requirements. I guess most vegetarians wouldn’t bother filling it out. Perhaps a future con could explicitly ask if attendees are vegetarians or vegans (or other common dietary requirements — I’ve noticed airline food using a list of common options which might be worth investigating).

At academic conferences I’ve estimated that vegetarians make up just under 10% of attendees. I’d take a guess that a con would probably have a higher percentage of people with particular diets.

I did notice that the breakfast-in-bed menu at the Cedar Court included Quorn sausages as an option, and when I asked for some at Monday morning breakfast they happily produced them (along with the comment from the serving chappie that he enjoyed eating them at home!).