Ok, it's a little bit tricky but possible in normal mode. I think it's nearly impossible in higher difficulty modes because there are simply too many civilians walking around the alarm buttons, and you can't keep an eye on the three at the same time (especially on the bitchy one nearby the staircase).
To do so, after you took care of the video cameras, immediately jump on the welcome desk and spam your yelling key (default: F) to get everyone down. Also aim at the AI and spam again to force them to get closer. Try to get at least one of them behind the desk. Use this method when you have to walk away to take care of the guard, of the maintenance guy or to set up the fake sentries.
You'll have to time it well; you want the AI to stay behind the desk while you are away. So call them and then run where you have to go; you'll have something like 10 or 20 seconds before they reach and then leave the position you gave them, trying to rally you, and therefore giving the opportunity to civilians to push the alarm button.
After this sneaky sequence, you won't need crowd control anymore so it should be okay.
