Gender Yes although there are a lot of ambiguous names in common use. Kelly, Ashley, even Lauren and many others. Sue might be a hard sell but there's always the old country song.

But I don't see how they could determine ethnicity from a boarding pass. There are a lot of people with names that don't match their appearance. Scott Fujita, a former NFL player would was adopted by a Japanese-American man and his Caucasian wife. I'm sure I can think of others. I know many Hispanics who don't really look Hispanic including some blond blued people and of course most African Americans have European names but if there is an issue out of a group of 50 I'd imagine a little BP swapping would take care of any issues, if you were willing to commit "ticket fraud".