Just an FYI. This is really not "new". Disney has had this for a VERY long time at the Contemporary & Grand Floridian in the daytime. They are just now expanding it. Calling this "dumping off your child with a babysitter" is like calling The Magic Kingdom an expensive movie. Disney already has babysitters available if you want them and they come to your room.
Kids play without adults all the time and no one even questions that. It's a child only experience, an adventure for them, and in their mind, they are "on their own" finding pirate treasure. This experience may be remembered more than anything else at Disney.