Just spray the back room (where one of the managers are) with an smg or rifle and camp there for a bit as you mow down the guards that try to get to you. Slowly creep out while taking out the other guards out. The guards blend in a lot with the walls so go
![Whee! :whee: :whee:](/styles/default/cag/smilies/whee!113.gif)
with the auto aiming so you target everyone around you.
AFAIK the other managers will run out the building and get to a vehicle, but won't actually drive off until you get outside the club. I took my sweet-ass time in the club, and when I went out the two remaining managers were already in a vehicle and tried to run me over. Didn't work.
![Stick out tongue :p :p](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)