It is very important that a child or young person make their decisions.
It can be important for a child/young person to make their own decisions (for some things) because if theydon't, they will grow up thinking other people can just make their decisions for them. Also, it depends on what decision the child is making. If a child is deciding whether or not they will do outdoor activities, then that should be up to the parents since the child can get hurt. Some kids don't know whether something is dangerous to do or not. If a child is deciding what their favorite color is or what they like to do in their spare time, that is a good example of what they should be deciding on their own.
So they can learn how to make decisions on their own when they grow up, they eventually have to make their own decisions. It's important to teach a child how to make their own decisions so they will be ready when they're on their own in the real world.
While it <em>is</em> a word to say when you don't know what to say, it doesn't <em>mean</em> anything. It's just a nonsense word popularized by Mary Poppins.