You might give a try to talking to the Luxor -- it's right next door, owned by the Mandalay Group, and there's a walkway over there in case of inclement weather if I remember right.
I was just flipping thru an airline vacations magazine yesterday on the plane back from Vegas, and surely with the so-called Mandalay Mile (their term, not mine), they should be able to accomodate you with something that works.
And if you're doing an invite only thing, you might want to really consider moving it to the Luxor, those things tend to grow totally out of hand if they are on property and it makes it hard to say no to people so you end up with 120 people showing up to eat and then no one's happy.
I learned that one the hard way a show or two ago as well
