Vegas and pregnant.

So I just found out I'm pregnant and according to the app I'm 4 weeks. This time next Friday I will be in Vegas for my 25th birthday with my cousin and some friends. I feel like now it would be a waste to go because of course I want to drink. I'm don't want to not go because I have never been. My boyfriend said "that's easy, just don't drink" lol but what's the fun in that? I still want to enjoy myself but should I tell the group?