I need to lose 20 pounds before Aug 10th?

I just had a baby via csection. My whole pregnancy i gained 50 pounds. Within the first 2 weeks i lost all my water retention, which was 31 pounds. Now i have 19 pounds to lose and i have a wedding to go to and my whole family will be there , some in which i havent seen in many years. I also have this one aunt that is constinatly bothering me about my weight. I was thinking about going on an all liquid diet. In the morning eat a banana juice, then jello chicken broth. If i do this everyother day for the next couple weeks, whats the most i could lose. Also i do plan on walking around my block