MultiQs lets you create multiple instant watch queues for Netflix. This extension lets you easily add titles to your queues from within Netflix.com. While in Netflix just right click on the image of the title you're interested in and select the queue you want to put it in!
In addition, some have asked what the point is of creating queues for their children to filter out inappropriate content if the child can just go over to Netflix.com and browse everything anyway? This extension addresses that as well. If you wish, you can use this extension to deny your children access to Netflix.com - they will instead be redirected to their queue within MultiQs where all content is filtered as you define.