??? Alcohol

So I'm very very early in my pregnancy but because we have had multiple miscarriages (the family knew and I did not drink) we dont want to tell any one until atleast 15 weeks maybe even later . (We lost twins at 13 weeks)

I don't want my mother in law to figure it out and she's kind of a big drinker ( not get hammered but she enjoys drinks). I'm well aware that alcohol is no good while pregnant .

I'm wondering if I have one beer during our weekly visits ( so once a week ) could that have a negative impact or is that a safe amount ? I'm thinking maybe mixing the beer half Clamato ?

I want to do what's right but I also don't want the world to know just yet .

Help