Find out if they drink wine or booze. Wine for the mother, a good bottle of Johny walker Red for dad.

LIE about your age or just don't bring it up. Lying always worked for me. it gets a little tough to lie when you are a couple years older than dad though. lol

Even if they say it's OK DONT sleep in the same room and if you have no choice DONT have sex with here there, unless they are gone; it's disrespectful and they will know.

Does she have a younger sister????