Finding out gender at 15 1/2 weeks?

I'll be getting a sonogram at 15 1/2 weeks and it's at a 3d/4d place...they said they can tell gender as early as 14 weeks! We are having it done then because we really want to be able to tell our family on an annual family trip...everyone would be there! Anyone have experience with finding out this early and how accurate it is?? I'm definitely worried they might tell me the wrong gender lol!!