A full charter can do just about anything they want, for a price. If they want the Lido closed 24/7, they could do it. Not saying they are in your case, but they could.
I would say you need to wait until you get on board and find out what is happening.
A charter is a charter. Anything less than a charter is a group ( possibly a large, medium or small group) on board, but it's not a charter. Chartered cruises "own" the ship for the cruise, groups don't change itineraries or shut down the Lido, they go the itinerary that was scheduled and use rooms or other spaces.