I looked at the Thomas Cook website and the ages are less specific. Nevertheless ages and associated extras became known at some point because cots and high chairs were placed in the apartments in advance.
As far as I can ascertain all reception staff plus all bookings staff would have been able to access the computer systems. They performed check-in and check-out procedures, some of which would require knowledge of extras owing. I can see no reason why access to certain areas of the system would have been restricted.
I don't see the relevance of controlling where the group were housed. It was near the Tapas, so what? Unless it was known at the time of booking that children were going to be left home alone every evening?
Let's see if we can clarify a bit. Are you working under the assumption that reception staff at the Tapas and Millennium had computer access? Under such circumstances there was no need for them to get paper reports. ditto the cleaning supervisors. I'm seeing paper reports printed the evening before to control these activities. Therefore I am assuming the OC did not have a distributed network. I do not know if you are counting those in your 12, but I'm excluding them.
The only ones with a legitimate need to update the booking system are those making bookings, those producing control reports, and the IT bod. I can't remember if there was a bookkeeper, who might or might not have access to reservations.
As to why allocation is important. First, from memory, that was done the evening before. No one who had access could know the location in advance of that, with exception of those who would do the allocation.
Second, why is location important. I have yet to see any evidence of those guests located 100m plus from one of the two restaurants doing a listening check. The Carpenters in Fiji Palms took their children to Tapas, as did other guests. Others put their children in the crèche or hired nannies.
If the T9 had been 100m plus away as the crow flies, or out of eyesight, would they have used a listening scheme? Or would they have thought it too risky and picked any of the alternatives, including take-aways (Berry+Balu), crèche, nanny, take kids to restaurant.
Blocks 4 and 5 look visually safe, in the sense that the apartments being above the Tapas can be seen. I am not arguing how much the McCanns could see, merely that there is a false sense of security in being able to see the rear of one's apartment.
I don't think you get a decent view of block 6 from the Tapas restaurant, but I cannot be certain. And I know very little about the layout of the Millennium.
I don't know the working range of the Payne's baby monitor, but I suspect it to would fail at much over 100m, due to obstacles in the way.
Plonk the T9 wherever in the OC is farthest from those 2 restaurants and the T9 would have been forced to scrap the listening idea. The myth of the visit to Chaplins fails for that reason (and others).
It's not those who make the bookings or produce reports that have control. They have knowledge, but not control. It is those who determine the allocation of customers to locations that are important. They have control.
Let me repeat. I do not have proof of this happening that would stand up in a civil or criminal court. I am merely pointing out a major weakness in the OC system, that a major change in 2007 was the MW booking info, and that Madeleine's disappearance happened relatively shortly after this change.