Can I just say that in most Mark warner resorts there was a nanny listening service, where parents woudl go out for the evening and leave their children in the rooms, and every half hour a nanny (norammly a young person with a childcare qualifation) would listen outside the door for signs of crying. Thousands of people used this service every year. The resort they stayed at did not offer this service as it was so spread about te village, so the McCanns just did the checks themselves.
I think it was a foolhardy thing to do, but I can see why people would get sucked into thinking it was safe.
I think it is more likely the man responsible for the other attacks in that area (one hour area) on british children on holiday (eight children woke up to find a man in their room, and in five cases he got into their beds and sexually abused them) is responsible for the disappearance.
As for the calpol, there was never any evidence put forward that this was the case and tests showed the McCanns were not medicating their other children. And if it was why not say she got hold of it and drank it herself. I know when I was a kid I loved the stuff, so it is reasonable to think a child would guzzle it down if they found it (child proof caps do not always work in my experience). Why launch a huge cover-up, get over ten witnesses to lie for you, get the british police and forensic service to lie for you when you could just say she drank the calpol herself?
And as the kids club staff at the resort all knew the children as they looked after them everyday, they were able to say they had looked after madeleine on the day she disappeared, and people confirmed that the photos of madeleine taken on the day she disappeared were real and they could confirm the situation occurred (i.e collecting tennis balls, and sitting with legs in the pool).