In the resort at the time? Which families please?
So, were this 38 year old couple intelligent controlling professionals or dewy-eyed naive dreamers? Surely they couldn't be both?
Naive;
too willing to believe that someone is telling the truth, that people's intentions in general are good, or that life is simple and fair. People are often naive because they are young and/or have not had much experience of life:
http://dictionary.cambridge.org/dictionary/british/naive
The thing is the McCann's are human, and humans don't always make the right decisions. They are both intelligent professionals and both do their jobs extremely well [did in Kate's case] that doesn't mean they are perfect.
You have Police Officers who know speeding in cars is against the law, yet you have Police Officers who speed, drink whilst driving etc. etc.
The McCann's thought their children would be safe, they had been settled into bed they were asleep when they left them, they were checking on them regularly, there was no 'intent' intended.