lullaby layette jacket

I am making the jacket from the lullaby layette pattern, which is a quilted baby jacket. Now, because I am being lazy, I purchased a quilted fabric for it. My question is how to approach the sleeves; they are drafted with a dart that goes up to the shoulder seam. As the pattern is written, one sews the dart on each layer of the sleeve fabric then puts the layers together. My problem is that my layers are already together! Should I try and take apart my sleeve pieces and put a dart separately in the top ad bottom, or just sew one dart and have it be on the inside of the sleeve? Of course I imagine that there will be some bulk in such a dart. Opinions?