Sounds like it's going to be gorgeous!
Did you mis-type the sateen dimensions? did you mean 5 yards of 108" instead of 18"? If your fabric is only 18" wide you won't have enough. With your sewing background, you probably already know this, but, sateen can be a bit tricky to work with because it has more of a stretch than regular quilting cotton and although it doesn't have a true nap, you do have to pay attention to the direction because the weave does catch the light differently.
I also like the lighter/darker version of the same color for the frames.