The world of virtual reality is changing quickly, and no one knows for sure how things will shake out. At present, most of VR content is being created by big companies as advertisements or experiments, but there are a few companies experimenting with educational content.
Making Google cardboard viewers is a pretty standard Makerspace workshop activity in universities, but it requires laser cutters and special lenses. Open source software to create VR is still being developed.
So it might be a bit too soon to add a VR “making” component to your elementary school Makerspace, but you can have a small set of viewers on hand, made from kits. Then students and faculty can learn about VR as this trend grows.