He would probably brief about it. Send up a few trial balloons about the venue and the time. See the reaction.
Then his colleagues who want something else would leak about the beer they wanted instead.
He would then announce it. But then forget to include someone. Or forget that another important event was on like a wedding. So he would need to give more details.
Then he would refuse to answer questions from one of the more perceptive family members
But lots of his supporters would say that the invitation was perfectly clear and we all now what would have happened if someone else Corbyn had tried to organise it and just look at the support he has.