just shoot it in raw and get a consistent exposure in camera to start (you only would need one image to create the HDR look).
Then take the image, set the exposure for, say, the background (maybe deep sky, dark, rich grass), then take another instance of the image and expose it for the subject (couple).
Stack them in photoshop and mask what you need and you're done!
For an action/script, Unique Images is selling their script for this
here (costly, but quality, I think).