Virtually all of the hotels in Vegas, at least those that have casinos, will gladly take your bags at the bell desk, whether you're staying there or not. It's customary to tip a dollar or two per bag regardless of the reason. I did this at New York New York once for a few hours before catching a flight. They even took my small bag to the front of the taxi line and loaded me in.

By the time you land, get bags, get to the hotel, it's going to be noon or later. Go to the checkin desk; it's quite possible they'll be able to give you a room early; if not go ahead and check the bags. You can kill 2-3 hours easily with lunch, a bit of walking around, perhaps a drink and some gambling.

I got a room at the Venetian at 11am once -- arrived at 10, and they took my cell # and called when the room was ready. Not guaranteed, of course.