It is an annual dinner. This is the 5th anniversary charity dinner with only vegetarian meals served. So, I'm not sure where should I place the word "vegetarian".I agree with Keith but, by the way, I am wondering if it's the fifth anniversary of something, or simply the fifth (annual) charity dinner.
Noted with thanks, Hermione!I agree with Keith about that point. If it's a dinner to raise funds for a charity, then it's a 'charity dinner' and we wouldn't put anything between those words. I don't think anybody would read it as a dinner for a vegetarian charity.