Killing the Parents
When writing for children, authors often have to get the parents out of the way so the characters can act independently. The most used (and now cliché) way of doing this is to kill off the parents.
Some authors find other, less violent ways. I enjoyed <em>The Railway Children</em> by E. Nesbit. The mother was busy writing to earn enough money to support the family, so the children were left to their own devices. The children obviously loved their mother, and she seemed like a pretty good mom.
In Harry Potter, the kids were all sent to boarding school. They had to deal with adults but not their parents (for the most part). At the same time, the parents were pretty awesome. I mean, Mr. and Mrs. Weasley are just fun. They loved their kids and did what they could to protect them.
So, parents can be cool in kids books. But they have to be out of the way a certain amount for the kids to be able to affect their own futures.