4am is during the night! It sounds like a nice trip. I would say that staff members should not be entering the children's rooms unless there is an emergency or poor behaviour. if you have a member of staff supervising the corridor, I would say that you need to negotiate a chair from the hotel. You may need to adjust supervision rosters so that staff who have covered the most inconvenient times get a chance to catch up on their sleep. As others have said, unfocused criticism is unhelpful. If the head says that there is inadequate supervision, they need to tell you what to do. Maybe they need to come on the trip.