You can walk through the casinos with your teen, but s/he may not stop near a machine or table (as in to wait for you while you bet). That's not allowed.
I wouldn't say that you'd want to swim the end of November. Last Thanksgiving it was very cold, and we had a rainstorm (but the rain is not typical for that time of year).
You could go to Red Rock, Hoover Dam, etc., of course. If they like video games, why not introduce them to Pinball. There is a Pinball Hall of Fame, where you can play games for 25-50 cents each. There are close to 100 games available, its really cool. If s/he bowls, there is bowling at Orleans, South Point, and Sam's Town. Also movies at many places, most of them casino related.
There is the mall, too, of course. Most teens are "mall rats." Showcase Mall on Las Vegas Blvd, but also The Galleria in Henderson, which is a more typical suburban mall.
There are many interesting museums, and other things to do. You can park on Sunset near Las Vegas Blvd (it is a marked parking area) and tune your radio into the control tower to watch planes take off and land.
You can take your teen to In and Out Burger if they've never been. They sell T-shirts, too.
Look at
http://lasvegal4locals.com for many more interesting ideas. There are many shows which are teen appropriate, too.
Fern