I'm sorry but I agree with Joe on this one. Whlist I can't imagine what they've been through losing a child in this way, I simply can't defend their actions. There are no two ways about it, I would not even leave my 3yr old daughter and 7yr old son locked (or otherwise) in my own house to 'nip' to a neighbours house for five minutes. I certainly would not leave them to go out for a meal and not in a hotel/apartment/holiday complext and not in a foreign country.
You see all these disclaimers about hotels not guaranteeing the safety of valuables left in your room - why would anyone assume its safe to leave their children? You have absolutely no idea who has access to your room when you're on holiday - the cleaners can let themselves in as and when they like...