I'm tying to decide the best option.  

I love red Rock but haven't been to the lake in a long time

Better get to the lake before all the water is gone!

...  and so do my doggies!  
 Have fun pretty lady.

It depends on how outdoor-sey you are. Grand Canyon is great by helicopter if you're feeling flush and have most of the day to play. The lake is a nice time if your going with friends. Skiwi rentals in henderson was good to my crew.  If its just you and you're pressed for time I'd vote Red Rock, especially if the weather is nice. Its only 20min and you could be back in the casino for table games by early evening. (I'm hoping the weather turns nice. I'm in the northeast  and it was F-ing snowing yesterday Have fun!

There’s a tour with lunch included and get picked up from the hotel lol! It seems to be the better option for hike