I am going to use my workplace as an example, since I don't have very many vegetarian people in my social circles.
On Fridays in the summer we often order pizza. We have 10 omnivores, 5 vegetarians and 2 people with celiac disease.
We order a gluten-free pizza for each of the two people with celiac disease, as they are small. They get their own pizzas and are not expected to share.
We order three supreme (two kinds of meat with green peppers, onion and black olives) pizzas, three pepperoni pizzas, and three vegetarian pizzas. The vegetarian pizzas are the first to go.