I'm catching up on all the stories I've missed by being offline this month and had to comment on this one. Jo, you did a great job with this story.
I was pleased at how you handled their accelerated relationship. You explained their getting together well, and it made for a very sweet story. I didn't think the WAFFs were too cloying -- in fact, I thought you did a nice job showing the fun side of their early relationship, when they aren't quite sure where things are going to go but are having fun keeping it a secret. Very fun, romantic and sexy.
But as others have mentioned, I was confused over the epilogue. You did a great job of setting up a fun short story, so I didn't understand why you would choose to suddenly change paths. Strictly from a writing standpoint, it takes the reader out of the moment you just spent pages working to set up ... you shot yourself in the foot, so to speak. A lighter touch may have accomplished what you seem to have been going for -- say, a great, great grandchild dancing through the fields, picking wildflowers to place on the joint graves of her ancestors, which show a long life and the song lyrics they loved so much -- but I honestly don't think even that is needed.
Bottom line, ending it with the revelation fits with the tone you had worked to set up initially. If you want to write a more angsty story, you clearly have the writing ability and story-telling talent to do so. So my advice would be to tackle that project in your next fanfic and not try to cram both into the same short story.
Hoping to see more from you soon,
Kathy