Great idea - if you guys wind up with fewer people and want a condo/apartment type thing check out:
http://www.oakwood.com/location_search.jsp (Mandalay Bay's zipcode is 89119.)
They're easy to deal with and the property on 85 East Agate - is brand new condos gated and look very nice. I drove by them a few weeks ago and talked with the guard at the gate. Rate for 2BR at that location $132/night so house with more people would probably be cheaper but still a reasonable deal and a very nice looking place.