I had a similar setup in my last place and ended up using soundproofing insulation plus doubling up drywall with Green Glue in between—worked better than I expected. If you're aiming for solid results without overcomplicating it, I'd suggest checking out...
I made a photo slideshow of our campaign highlights—maps, character art, funny moments—and uploaded it to a digital frame from www.nixplay.com. Gave each player one so they could relive the journey anytime. It was a surprise hit, especially since I added some inside jokes and final quotes from...