I see that this has quickly gone off topic. That seems to happen a lot lately. To answer the question asked... you can opt out of the scanner and request a pat down. No you cannot pick who does it.. it will be the same gender as you are. You can ask for a private area and they will comply, you at the same time can have a witness of your choosing and they also will bring a witness of the same gender as the person getting patted down. Enjoy your vacation.