Work outing coming up that involves drinking! Not sure what to do...

I'm currently 5 wks 2d. Next week Thursday, my job is having a "pedal tavern" outing. This is where a group of people ride a multi-person bike to different bars and stop to drink along the way.(I live in WI. We like to drink) My dilemma is, that I want to go-and not drink, but I wasn't planning to tell my job about my pregnancy until after my first ultrasound where I hear a heartbeat. Should I make up an excuse to not go? I rsvp'd over a month ago. Does anyone else have any ideas??? Help guys!