Lie to my parents or Cancel my trip?

IM
I booked a 4ngt trip to Vegas with my ex. We are fwb and we understand those terms. my parents are religious/strict so theyllbe asking too many questions about me leaving home for 4 nights. I was planning on telling a lie.  It's the only way I can go. Should I cancel the trip or go on the trip ad enjoy myself but lie to my parents? I'm 24 btw.