First Appt this week-test question

Margaux • Baby Matthew born on 12/3/15...new Mama alert!
I have my first regular OB appt on Thurs. Will be 10wks and I'm guessing they will start asking if I want to do any of that crazy testing. I was under the impression that Twins you aren't able to tell gender so early. Does anyone happen to know if that is true? Also trying to decide if genetic testing is worth it considering all the false positives that seem to happen.
Curious to know what you all have done/think!  Thanks! 😀