One thing I would suggest.... Get your wife and daughters to cook together, film or document the recipes. Make those meals as many times as you can with them. It's one of the things that continues to live on after a loved one leaves us, the memories of making meals together, combined with the family recipes that make them unique and special. Every time your daughters then cook that meal or recipe, they will be reminded of their mother.... And as they pass those down, they will pass down the stories as well.
And as others have stated, keep up hope. Miracles do happen.
I wish you all the comfort that your family will be able to receive in these trying times for you.