Keeping it a secret!!

This is my first pregnancy- I'm 6 weeks 5 days today. My best friend gets married on Saturday. I already told her the good news (I knew she would spot me not drinking on her hen do and didn't want to make a fuss on her special day!!) and she was thrilled, and helpfully drank all the drinks that were bought for me on her hen do last weekend- sneaky!! but I'm bridesmaid for her along with two of our other friends that I haven't told yet. Her parents have bought so much fizz for us to drink while we get ready- how am I not going to get rumbled?! I love a drink and if I'm spotted not actually drinking they'll know- which isn't a huge deal in itself but again I don't want to steal any of the lime light!! Any ideas? There is no way they would buy the old 'im on antibiotics'- they know me better than that!!