So I went to the pantry, and we came up with our own version of the craft. (I'm sure the one at school would have been cooler, but we had no idea what we were doing and just made it up as we went. It didn't turn out too badly though.)
Then we used white glue around the edge of cup and stuck it onto a white foamy plate.
Paint another ring of glue around the cup above the first layer of marshmallows, add marshmallows, repeat, repeat, repeat...
He kept going and going, and when the cup was covered, he had his igloo. He enjoyed making this one so much, he dug out more supplies and made one for each of his siblings.
Another tragedy averted!