I went a few years ago but stayed in the Luxor. There is sooo much to do there, besides gambling and drinking ha. I would suggest seeing a show (there are always new performances), and definitely visit the M M factory! Good luck! Hope you have a great time :)
You will be allowed up to 4 people per room, but you might have to pay extra for the extra 3 people. 3 rooms might be better.The pool at Mirage is pretty nice and Bare is a lot of fun, but if you are going between now and next March/April then Bare will be closed and the main pool will be pretty quiet and it will be too cold to swim or lie out anyway.
1-You are not going to get more than 2 keys/room unless you pay for the additional people. 2-The Mirage pool area is small compared to other resorts there (Mandalay Bay, Ceasars, HRH, The Palms). Room keys may need to be shown.