"From what you gather the event has been cancelled....."
You do have a right to ask exactly when this will be happening you know.
You need to inform yourself of your own parental rights, you do have them. Ask a lawyer for advice if you need to.
Your son may hate you for stopping him at the moment and could send him running into the loving bosom of the borg. So it seems like you're damned if you do and damned if you don't.
So you need to decide what you would prefer to be damned for - trying to get him to postpone or letting it go ahead and hoping and waiting for him to wake up himself.