That's a big quizhee, and that means each of you moved a LOT of snow!
I bet it was a blast for the kids ... and for you.
Our cut-off temperature for sleeping in quinzhees in our Outdoor Adventure club at the school I teach at here in Manitoba is anything above -3C (about +27F). Reason: a school group in Ontario lost 2 of 4 students who were in a wet quinzhee collapse disaster that happened after students and leaders were sleeping. I don't know the details - the Coroner's Report has yet to be published - but it sounds like both the temperature and the shape of this quinzhee may both have played a role.
Of course there are many other factors besides outside temperature and shape that are important when it comes to snow structure stability, too: types of snow used, prep. of site, how well the snow is "worked" before letting it sinter, temperature gradient in snowpack, humidity in the snowpack, length of time after piling and before excavating, temperature change between piling and excavating, amount of direct sun, being on ice or on land, excavation procedure .... it'll be pretty interesting if the Coroner reports any recommendations.