I had an ivory dress. I went with black magic roses and it looked amazing against my dress. The color of the roses went with my other colors though. Here's a picture so you can see how dark flowers look against an ivory dress.
You're overthinking. Like Southernbelle said, these are both neutrals, so anything will work. My dress was ivory lace over a light champagne color. It's basically white - it goes with anything. My bouquet was white, peach, and yellow.
This was my bridal bouquet. My dress, like yours, was champagne and ivory> I used garden roses, dusty miller, hypericum berries, blue hydrangeas, and my favorite were white anemones. They are the white flower with the black center. They were really difficult to get, but looked amazing. White roses always seem to have an ivory color to them, and champagne is a neutral, you can add any color to them and it will look beautiful.
Re: Best colored bouquets for a champagne and ivory gown?