I am so sorry for your loss. These pupps become like children and it is impossible to make the pain go away. Try and be strong. My family had a golden retriever about five years ago and she was a beautiful happy, perfect dog - unfortunately - she got hit by a car, on our VERY quiet country road.
You could tell your young daughters she was simply too perfect and had to go to heaven to be with the other angel dogs.
I'm not much help - but I am sorry for your loss!