I am sending prayers your way as well. We "kitty" mommies need to stick together! I had both of my boys neutered and declawed at the same time. They were both fine after two or three days. Your girls will will be sore for a few days and sleep alot. They seem to bounce back pretty quickly, though.
Did your vet tell you to use paper litter when they come home? It is not as irritating as the regular clay based litters.
I would not be too sure about your vets prognosis. I think that your regular vet needs to see them (when healed up of course) and evaluate what (if anything) may be going on with their hearts. Maybe his EKG machine needs to be re-calibrated or something?
They look really adorable. I know that you are looking forward to having them both home, safe and sound.