Hoover Dam and Red Rock is where people go after losing all their money. GC is kinda far, it's a good 5 hours to the South Rim. A little less to the west rim where the sky bridge is located.
Top of the strat is cool, bring beers with you, they'll let you take them in the elevator to the top.
Bellagio Buffet is good, go at 2pm then watch the fountains. That basically becomes your lunch and dinner, rate is less at 2pm. Go at 4pm and you'll pay a bunch more for the dinner rate. It's basically the same stuff, they just add more sea food (crap legs).