When I was pregnant with dd2 I decided that I needed to separate bf'ing from dd1's bedtime routine (in anticipation of being away from dd1 when I gave birth/was in hospital etc), so I gradually moved it 'backwards' in the routine. So it started out being dinner, play, bath, story, bf, bed, then became dinner, play, bath, bf, story, bed etc etc until bf'ing was after dinner, and before the bath. I didn't need to add anything in to the routine either (eg. snack before bed) which was great.
Maybe something for you to think about, since you probably don't want to (sounds like) give up bf'ing... and 8wks would be long enough to work on this...
Sorry, no experience with not bf'ing just for one night. But I'm imagining it depends very much on your ds's personality. Since you're not going to be there, he might just forget about it??