Creating a widely accessible VR experience

Hello, I've got a client who wants to create an interactive VR art exhibition in the next 2 months for public delivery. They're open as to the delivery format (app or web hosting, which VR headsets to support). I'm wondering what the best option would be to suggest to them regarding distribution?

Whereas this job sounds achievable if I was supporting for just one headset, it sounds like it will turn in to a nightmare if I'm trying to deliver an app across multiple platforms, e.g. mac/pc with support for the Oculus/Vive/Windows VR.

I've never delivered a project using webXR, but it doesn't like it will deliver graphically, and even if it does, supporting multiple headsets and mac/pc looks like it will eat away at the 2-month time frame.

Are there any suggestions on what it would be reasonable to offer the client regarding VR distribution?