I haven't been in a while, but I used to celebrate with the family Xmas eve afternoon and fly into LV that evening. It's not as crowded, although it didn't seem that different in the locals casinos. The strip is relatively quiet though. Though most shows will be dark, you'll still find some entertainment as you move down the food chain. If decorations are your thing, you'll be in hog heaven. In addition to the strip, make it out to Sam's Town as they do a good job decorating the atrium.
One opf my best Xmas memories is of one year that I dropped my buddy off at the golf club he works for. The club is closed, but he vollenteers for any club members that want to play or bring guests for free. I came back a few hours later and he said it was busier than he thought it would be, so he'd be another couple of hours. He suggested I jump out for nine in a bit, so I did. Here's a Seattle boy, wearing shorts and a polo, playing golf Xmas afternoon. It was wonderful. I cut mine nine short though when the sun went behind the mountains (the butts up against Red Rock) and the temp dropped from about 60 to the high 40s in no time! I traded the golf cart for a real one with a heater in no time! When we got back to the house, it was cocktails on the patio before grilling some huge ribeyes for dinner. Not your typical Xmas afternoon/dinner in Seattle!
Good Luck!
Ric at Joes
