How to hide it from friends?

So I am super conservative bc I know the rates of early miscarriage are high. I'm only at 3w4d and already have had to avoid situations with alcohol twice by making excuses of a headache or upset stomach. It makes me not want to even be social at all until I can tell people. I'm invited to a friends pool tomorrow to just hang out, but I know they will be drinking? Anyone have any good ideas? Maybe I'm on a new diet for the next couple months? I was thinking the acid watchers diet. I have bad reflux anyway and it involves cutting out all alcohol. Help much appreciated from those who have been here.