Absolutely -- I'd bet your vegetarian guest would like many of the sides, etc. and your WP can give you suggestions of an entree that they'd prepare just for that guest. I don't think it would be a problem at all.
I am going to have to look into that, It just seems odd to have a buffet, and then have one person get served plate. But I dont want to leave him out food wise, so it'll have to work.
I agree with the previous posters who suggested that mimosas or bellinis or both would be nice options for that time of day. Because they are only part champagne, they shouldn't be too expensive. And Carrie's idea of doing bill on consumption for sodas & water (and possibly juice) would probably be less expensive in the end.
Good luck!