I've been avoiding posting on this topic in general. What happened is beyond sad and disturbing.
I feel though that the sentiment of your comment is correct. The parents responsibility towards the child can't be abdicated to some child minder irrespective of how convenient it is.
Quite frankly you could replace Dros with any of the other restaurants that operated on a similar basis: Spur, Papachinos, John Dory's, Panarottis or a multitude of independents with a play area.
The principle remains the same. A a parent your child is your responsibility.