Security cameras are fine - you may want to look into getting some IR light sources to mount on the stage.
I prefered to have quantity over quality - allowing me to (cheaply) put cameras in any spots that needed attention and use a matrix switcher (as I owned my own equiptment anyway). I would avoid the temptation to go for pan/tilt/zoom cameras as I have found they require frequent maintenance as their mechanisms get filled with haze fluid.