Scratch n sniff bacon deck seals are what we settled on, but they are prohibitively expensive ($2000+)...they are definitely a stretch goal but at the moment I'm not sure we'll reach that far.
A slightly lesser expensive option would be to get bacon scented stickers printed and then apply them to the outside of the cello wrapping, but that would have to be done by hand, and once the wrapping is removed, the sticker is as well.
Another option would be to get stickers made and include them with the decks for self-application by backers... would you guys be interested in this option?
-David