Have the girls been there before? If so, then yes, they could bring their friends & show they around town.
If not? eh. They could definately feel awkward many places........
My sons grew up visiting Vegas, but we did family activities mostly, when they were younger.
By the time they were old enough to venture out on their own.....they knew where
to go, & what they could, & couldn't do. They aren't big gamblers these days, due to budgets, but they
enjoy getting buffet comps, & freeplay, etc. (wonder where they got that from?) lol
Like I said, if its the girls first time?
I think College Graduation would make more sense than High School grad.