Vacation minus hubby & kids? *kinda long*

Has anyone taken a vacation & left the kids at home with hubby?? My mom has told me her & my stepdad want to take my step sister and I to vegas for our 21st birthdays. Her 21st is beginning of september and my 22nd is beginning of october, so we'd both technically be 21 if we wen't mid-september. My step-dad's father did that with him, so he wants to do it for his kids (and bonus kids) lol.

NOW my issue obviously is being away from my 3 & 1yr old and leaving them with dad & m.i.l for a few days (thurs-sun). My m.i.l is a tremendous help with the boys- they love her to bits so I 100% trust that between the two of them, they'd be able to do it.. I just feel like a shit mom for leaving them to go to freaking las vegas & I feel bad for going without my partner. He's invited, but he'd have to pay for his ticket, attractions etc. which we don't have the funds for aswell as without him at home, my m.i.l would not be able to do it alone as it's just her, and there's nobody else I trust my children with. I'm very torn.. should I go? Has anyone here been in a similar situation?