Man, as a fellow curator I wish you the best of luck with that. Shame to see such cool plants lying forgotten about. I came into a collection much like that.
I don't know what your position entails and if you're directly doing or in charge of daily watering, but that is a big, big part of keeping mexican pings alive through the years. I'm surprised they're not already dead, because they have such unique needs that the majority of people just overwater and kill em. Do you have greenhouse staff or is everything left up to the students?
In a greenhouse environment, especially since you're in the south like me, I'd suggest a 5-part mix for Pings. I like sand/potting soil/perlite/permatill/turface quite a lot, in roughly equal parts. Sounds complicated, but not when you mix it in large batches in a cement mixer. My mix gives them enough juice to grow, but the low amount of potting soil is cut with enough sterile stuff that it's actually not a lot of nutrients. And furthermore, most importantly, it drains enough that you won't rot them in summertime or wintertime.
And also, at least 70% shade from late May to late Sept here. It takes the edge off of our brutal heat. Hot soil will rot a mexican ping with Fusarium in a couple weeks.
Oh, and I know you're probably busy with everything, but once you are able to get a growlist together, drop me a line at kevintheplantman(at)gmail(dot)com. Might be able to improve the diversity of your guys' collection.