Mandalay is ok a nice hotel but right at the end of the strip. The Venitian is much nicer and right in the centre of the strip. You can reach all the casinos from here. I would really recommend the Venitian as the rooms are massive and are all suites. You wont regret it mind you with any lucky you wont be spending much time in your room as there is so much to see and do in Las Vegas.
You will love it.
Try to get to see one of the Cirque du soliel shows if you can either O at the Belagio, La reve at Winn or my favourite is Ka at the MGM they are brilliant and mind blowing.
Also try to do a trip out to the grand canyon by helicopter if you can. I know its expensive but boy you get a lot for your $$$ you can land on the floor of the canyon have a snack champagne and then get great view of the Hoover dam.
Enjoy its really fantastic.
Gary