Prevent discounted gift certificates

As an opening offer we would like to give a 5% discount off everything except gift certificates. I’ve set up a cart promotion that gives 5% off the order subtotal. I wanted to add a condition to exempt gift certificates but it doesn’t seem possible. Does anyone know if it is or if there’s any other way to do this?

The way I would do it would be to create a cart promotion equal to discount of 5%, then add the bonus discount on products or categories depending on how you set it up. Personally, I would put the gift cards in their own category then add all categories to the discount except the gift card category and you should be set.

Thank you. I’m probably being really thick but I can’t see how to do this. I’m referring to the gift certificates produced via the gift certificate addon. I can’t see how to put these in a category or refer to them in a promotion at all ??? What am I missing?