I adore churrasciarias, but they are simply not the ideal place for a vegetarian. It's meat-centric and very "in your face" meaty goodness. They do have a salad bar, but for goodness' sake, who wants to be restricted to a limited salad bar while everyone else has a full meal, on their birthday?!
Shoot, for my own birthday dinners, I make sure to choose a place that is GF-friendly for my mom. I would in no way attempt to take her to a place where, say, everything is flour-battered for her birthday.