You're going on a 7 day fast in which you drink all of your calories? How is that a fast? Fasting = not consuming calories. Drinking calories =/= fasting. Am I missing something here?
^This. You're proposing an all liquid diet, which some people enjoy from time to time. I have a word of warning though - even if you use a blender to blend up whole fruits, the lack of fiber in a liquid diet will make your digestive system a little upset, and you'll have some pretty unpleasant, incredibly dense bowel movements.
If you still want to try it out, I recommend adding some kind of powdered fiber additive to your drinks to help keep things moving smoothly.