Based purely on nothing but my own head canon I've decided that Good Omens: The Movie is going to be 15 minutes of setting up and defeating the next threat to humanity while Crowley simultaneously rescues Aziraphale, then 75 minutes of Crowley and Aziraphale planning and attending their wedding in Hogback Wood, which is Adam's Garden of Eden. Adam will perform a small miracle to make his parents feel like they've known Aziraphale and Crowley for many years, otherwise they're going to wonder a bit too much how their son knows two middle-aged strangers well enough to host their wedding.