Aim for one of the newer hotels and you will be fine, we usually stay in the Bellagio when we go. we usually do a week when we go as there is so much to do.
there are hundreds of top class restaurants, Bellagio alone has 2 Michelin star restaurants.
loads of shows to go to, if you dont mind what you see you can use a service called Tix4Tonight, they have a number of booths dotted about where you can get tickets for 40/50/60% off for that night. odds are you wont get the really popular shows in there but you never know, I think we got Jersey boys tickets through it.
Grand canyon is a must. I'd suggest as early in the day as possible in September tho unless you like it HOT!.
One bit of advice I would suggest is to take a small bottle of fabreeze with you, its a proper culture shock to go somewhere that allows smoking ( all casino's ) and if your not used to it you will feel like you stink of smoke by the end of the day. so fabreezing cloths just freshens them up from that a bit.