Hi Punter
My experience with LV shows is to book in advance, direct on the relevant hotel site (rather than re-sellers) if you are going weeks in advance. I see you are going next week, so I feel that the only seats available on line will be poor ones. Therefore, I would wait till I got there and go to the ticket office a day or two before the show, and you should get a seat (unless its Celine or such like) Also, early in the week (Mon Tue Wed are obviously less crowded, but some shows are 'dark' (not playing) on maybe Tuesdays.
My personal favourite show is Mystere at T.I. Hotel (former TReasure Island) This is an absolue knock-out show (a bit like a circus olympic standard gymnasts, acrobats etc) Tickets are about $95, but you will come out saying it was worth every penny. I have seen this show, with different people, 4 times and I am gob-smacked every time.
I assume you have ahotel booked, but if not I find Mirage or T.I very good especially in terms of location. Hotels at either end of the strip, say Luxor or Statosphere are just too far away from the action, and require a taxi every time you go out.
Enjoy your trip.!