If your looking for the no kids option then many of the pools have a ultra pool or european style pool area, this would be no kid friendly. A few of the better ones are Wynn, Venetian, Caesars, MGM Grand, and Mirage. You'll need to look at your price range for accomodations since these hotels vary in price
Here's some virtual tours of
Las Vegas Pools
and here's a page with
promo codes for deals on some of the Las Vegas Hotels mentioned.