Here is a reply letter to a hotel employee recently who asked for my advice on the matter:
As the owner of The Hotel Nanny my view point is somewhat clear and predictable on this issue. This aside, I am generally a person who is hyper-vigilant so I would be looking at this with all the worst case scenarios, and the first that comes to mind is fire. This could mean that the parents may be separated or unable to get to their children. You can only imagine all the possibilities connected to this. Also there is sickness, fever — all things that can come on very quickly in children. Normally we are alerted by such things by them crying or strange noises, or even the children/babies being unusually restless and then we as care givers are alerted and quickly react. If you are out of the hotel room for a few hours for dinner it can be a deadly amount of time. Sickness aside, I heard one story that parents had locked the children in the room, so to keep them "safe" but the toddler climbed out of the window.
In the worst case scenario and hypothetically — if a terrible thing did happen, there would be all the associated hype around the hotel which would also be brought in to a less than favourable media storm. However, this is a far smaller problem in comparison to facing a tragic reality of a child going missing.
I think, for me and again being hyper-vigilant — if the parents have made you aware of the decision to leave their children it clearly then makes you uneasy and without realising displaces some of that duty of care on your shoulders, knowing the children are alone and unsupervised. Of course I would never encourage this scenario and children always need a professional carer or parent/family member with them. However, I think it is important that the hotel sets out what the house rules are for such matters so everyone is clear about the safety aspects involved.
I hope this helps