Subcards on stage are a general win in that they can provide some of the best aspects of both both omnis and cards.
If reducing the level of audience enthusiasm is one of the goals which influences the decision towards using cardioids, then consider a setup that uses less angle between the mics. ORTF will pickup more crowd reaction behind the pair than DIN, and an even narrower angle (usually with a slightly wider spacing to compensate for less angle) even less so. Think of the overall sensitivity of the pattern as a pair to sounds from behind, verses thinking of each mic pattern individually.
One useful trick I like to do if I have an extra channel is to tape a single miniature omni onto the surface of the stage (boundary mounted) a couple feet in front of my stereo pair of cardioids. That extra omni channel can be very useful to fatten up the bottom end, firm up the center of the soundstage and also provide a bit more 3-d image depth. I bring it up in the mix just enough to see if it helps with those things, and leave it out if it doesn't. I just need to make sure it is protected so it doesn't get crushed if accidentally steped on.
The 'couple of feet' thing is intentional because I want it far enough away to not get problems of being sort of near-spaced but not exaclty coincident with the main pair. By placing the omni farther on stage than the main pair I get two advantages: it's positioned slightly closer to the sources so the direct/reverb ratio of the omni, already improved by the boundary mouning, is closer to that of the directional pair, and secondly the distance somewhat decorrelates the signal from that of the main pair so there should be less potential phase issues like comb filtering when the three are mixed together. I usually don't delay the omni to align with the stereo pair, but if I did, it would actually increase the decorrelation for sound arriving from directions other than directly in front of the omni (primarily the crowd and reverberance), while increasing the correlation for the direct sound arriving from straight ahead. That's my fancy sounding justification anyway, mostly I put it there just to get it closer to wehre I would want it alone.