3D Ultrasound

I'll be 17 weeks tomorrow and we are going in for a private ultrasound. How accurate do you all think the results will be? We have a lot of family in town for the holiday so we wanted to surprise everyone with a gender reveal. I just don't want to get overly excited if it's not going to be accurate. I had an appointment last week and baby had a heartbeat of 160bpm and kept moving around!