exactly!
When you go shopping for the fat quarters, have in mind a theme or color combination your wife enjoys working with. My favorite holidays (Fourth of July and Christmas) are always good for a theme ... or, I shop by my favorite color ... so many shades and ways to highlight blue, don't you know ...
you can see ... with a minimum of knowledge (what is her favorite color) about your wife (what is her favorite time of year?) your local quilt shop will be able to fix you up with a good variety of fat quarters to hide your gift card in.
Congratulations on being a thoughtful, observant husband, who cares enough to give her the best. You are a special person who can see your wife's abilities and enhance them. You are doing your job very well.