Mass catering can be hit or miss at the best of times.
Still, a load of crudités and veggie dips, falafels, crisps, vegetable samosas and spring rolls, cucumber sandwiches, vegetable kebabs, olives, pickled cocktail onions and so on - you might want to drop olives if you're going for low carbon, though. Like the sound of the mushroom vol au vents. Most buffets of any sort often don't include enough vol au vents (Ii.e. there are often none at all.)
Catered dessert options at my work were mostly sliced fruit buffet, and sometimes cake/biscuit options, so that wouldn't change.
Being in tech, there are some who would be horrified at any meal thst isn't mostly meat-based protein, but plenty are already vegetarian or vegan or at least do meat-free days a few times a week.
I've been taken out to a vegan restaurant with work colleagues before - it was excellent food and the world didn't stop turning. And I do eat quite a lot of meat, and grew up on a beef and dairy farm.
Eating one vegetarian/vegan buffet isn't going to kill anyone (unless they're severely allergic to a particular ingredient - and anyone who is is likely to be very careful about what food they're in contact with anyway.)