Replying to Help getting out of some trouble

hey, my parents found out that i had a kid over one night when they werent there (but in reality there was like 10-15 kids there that night). One of my friends had sex with his g/f on my sisters bed (fucked up i know) but my parents found a condom wrapper, and thats how they found out that more than 1 other kid was here. She asked who it was and i told her i didnt want to get anybody in trouble so she took my keys. Now what should i do? here are my options as i see it:

a. dont give the kids name who had sex on my sistes bed
b. tell my mom the kids name & get my keys back


i talked to the kid who fucked his g/f and he said do what ever you have to do to not get yourself in trouble, but also try to not get me in trouble.

what should i do?