What's the pie substance? If it's something soft / whipped-creamy and not liquid, how about using windscreens on the mics? They'll be available from the manufacturer and will provide a small element of protection, at least - probably enough to protect from errant blocking since you've indicated the mic-side of the face will be away from the pie.
Mics work by sound pressure waves impacting the diaphragm - if you put a material over the mic that prevents any air from getting through to the diaphragm you'll change the way the mic receives the acoustic energy. Normally it's direct from the user's mouth. If you add a hard barrier, e.g. plastic, the pressure waves will hit the plastic, then the plastic will transfer a certain amount of that energy on through to the mic's diaphragm. If the covering is even a bit loose you'll lose a significant frequency set on the high end as a loose covering will absorb more as opposed to passing it through.
That's in a vacuum though and also assuming the high end isn't getting cut out by a bad EQ, insufficient loudspeaker coverage, or an operator with an ear for the low-end (common in inexperienced operators). If you're in doubt the plastic wrap will definitely protect the diaphragm, but in my opinion you'll be sacrificing more performance than is necessary.
