I've been having trouble with large crowds myself in recent months.

Have you talked about your discomfort in crowds with your wife before? If so, I would think she would understand.

If you are anxious that she will be mad anyway--you know, the "you never want to do what I want to do" thing--maybe you can plan something with her right then that she would like to do that won't include crowds. Maybe have one of those free papers with your city's upcoming events handy so you can look at it together. That way you can demonstrate right then and there that you are indeed flexible about what kind of plans the two of you make together, and that you do care about how she feels about this.

(If I'm worried I'm going to make someone angry, it usually helps me to have a plan ready to diffuse the situation--particularly if I'm unsure of what their reaction will be.)

--Ceara1010