Hi Ruby,
The Marriott in Summerlin is nice.......you're not very far from Red Rock if you are going to have a car you can drive thru the loop & if you like hiking/walking there are trails. Mount Charleston is ok, just a mountain with an over prices lodge to eat at the top! (we go up there to get away from the heat in the summer-usually 20-25 degrees cooler.)
You are near quite a few restaurants........Kona Grill, Cheesecake Factory, Mimi's Cafe, Claim Jumper, PF Changs, and a newer one called Sandstone (I think) If you come to the strip,and happen to come to Wynn/Encore during the day ask for Kristie-it will be fun to see a "kindleboader"!

Being that I work in a casino, I am all for the lounging by the pool thing, also I hav heard that the spa there is wonderful, so maybe try that.
Anyway, enjoy-don't lose too much money.

kkjn