Here's some information that some may find interesting.
We holidayed there a few years ago. There are 2 complex run by the same company. The one where we stayed had a creche which was running at the time of Madeleine's disappearance, and was available for families at both.
We met a young couple staying where they had stayed, but were eating at our on site restaurant in the evenings, so they could put their little girl in the creche.
The apartment the McCann's stayed in was the last on a corner, on the road side. The restaurant they and their friends used was about 150 yards from the apartment, but there was not a clear line of vision from the restaurant to their apartment, due to the location of the reception building and also a wall about 7 or 8 feet between the reception and their apartment.
I distinctly remember when the tragic story first made the news, that the McCann's and their friends said the apartment was visible from where they were sitting outside the restaurant, so we were shocked when we went there and realised that was not the case.
I seem to remember that yes, the parents were checking on one another's children but the last one to check on Madeleine and her brothers, didn't go inside the apartment and saw the children, he opened the door and listened and hearing nothing to suggest there was a problem of any kind, assumed all was well.
I agree that who ever is responsible for this poor girl's disappearance is the villain but for me, the risk that was taken on several occasions is beyond my comprehension.