I need help lying!!

Kelsey
My close friend turns 30 this weekend. Of course there's a fancy dinner where I won't be drinking. Followed by my favorite champagne bar, where I won't be drinking (it's very unlike me to turn down CHAMPS), and then this weekend there will be zip lining, which I cannot participate in. 
I had a MC in March, and with that pregnancy, I told a lot of my friends, I just couldn't hold on the excitement! This time, I would like to keep it quiet until later. 
I can get to dinner early to order a mock tail, and then be the DD, but the zip lining?!? Any ideas to casually get out of it?