Thats awesome! My wife is a music teacher and conducts several community Bands. It's amazing the energy that the older musicians bring to performances. I think it's their passion and pure enjoyment of playing together that brings that energy. Best of luck!
I think a big part of it with this choir is that every person in the room actively wants to be there. In high school (band and choir) a lot of kids are participating purely for the easy A. In college there is far less of this phenomenon, but as long as it's a class, some people will not be giving it their attention or musical best. But this choir, from the Maestro on down is completely voluntary, with no reward (really) beyond excellence in performance. And I really like our director. This season we're going to be doing a full performance of Handel's Messiah, which I have never sang but is super old hat to all the veterans, and there is a tendency for those who know it to go on autopilot. But our director made a point to say that every time you perform a masterpiece, there is someone in the audience hearing it for the very first time, and someone hearing it for the last time, and those are the people you're really performing for.