HELP! THOUGHTS????

going to my future SILs Bach, I’ll be 11 weeks. Was planning on telling my best friend who is coming so she could help me hide it, I just saw itinerary and there is a wine tasting on the schedule. I don’t know how the eff to fake that. The MOH is the brides sister and has a big mouth she will def tell my brothers fiancé if I ask her to switch to another activity. We plan on telling our families the following week after my 12w scan. Unfortunately i know if I tell the bride to be she’ll tell my brother and we just really want to surprise everyone together after a big family dinner. I have no idea what to do ☹️