Whilst I'm all in favour of a degree of informality in meetings, poor chairmanship means it can be difficult to see what's been agreed or not. I favour the chair (or at least someone) summing up each agenda item with what has been agreed, rejected or is subject to further discussion so everyone is clear what you've actually done. Clearly this didn't happen in your case so I'd suggest proposing another agenda item at the next meeting to agree the practical arrangements for the public meeting that was, apparently, agreed in principle.