I see you were online today, but didn't comment. I do hope for your pup's sake you have put off this scheduled surgery for tomorrow.
I am praying you have made an appt for another opinion. I just re read what you posted about your vet saying how hard this will be on him.....I don't know what your reasons are but I am praying he doesn't suffer. I am not against doing both knees on a pup...I have certainly done that...but again only letting a boarded surgeon do it.