Do I need an editorial calendar, or is improvising enough?

Yes, you need a calendar built on the real gaps in service. Improvising only fits the story of a closure or a dish that ran out, on top of that calendar. Mark the real services on the week and leave one slot free for the unexpected. The piece is decided every morning, and by two in the afternoon the team can no longer film. The week is written with pieces, hours, and one slot left empty on purpose for what happens in the room.