Greenhut, I think you may have missed the point of RTBDiver's post, and granted using the words 'spoiled americans' can do that, but the issue he brings up isn't entertainment or disruption, or even weather a child/adult is pleasant to be around or not, it's distraction.
Boat Captains have an incredible responsibility for the safety of all their passengers, the status of their boat while at sea, and changing weather conditions that could prompt a recall. I believe his point was that the very nature of a child's enthusiam & questions, can be distracting & cause the Captain to possibly miss something inportant to his/her main priorities.
I know of a dive boat that sank, while divers were in the water, because the Captain got off the boat (at the mooring) to snorkel with a passanger. In the meantime the through hull fitting busted, the boat took on water. When they looked back the boat was gone & the mooring ball was being pulled under. No, that's not the norm, but it shows what 'can' happen with just a few minutes of inattention. The Ocean can be very unforgiving.
I think his point was to check with the resort if you're not bringing a caretaker with you or won't have a non-diver staying on the boat with such a young child. They usually have a staff member with a day off willing to make a few extra bucks that would help keep the child entertained, and leave the Captain to monitor his responsibilities, rather than try to split their attention.
Could be wrong, but I've seen what can happen too often when a Captain is distracted, even for a few minutes.