Today I noticed new sections for Movies, TV Shows, and Kids on the Library tab of my Shield TV. Movies and TV shows are populated, but Kids is empty (and I have plenty of kids recordings that should be showing up).
Have you checked out the documentation relating to the Kids section:
You may need to manually add a few things to it in the web UI.
You'll need to adjust Library Visibility for content to add it to the Kids Section.
We're working on a way to let Channels pre-populate your Kids Section for you, to give you a head start. It should be in the next release.
Also, check out the new Enhanced Library Browsing, if you have a large library.
It turns out I just had to disable and re-enable the Kids section for it to add my content. Since I had already enabled it before the new feature was added, I guess it never had a chance to populate.
Yes, turns out the populating action is already in there 
Be sure to go over it’s choices. It’s a good start but you may have different opinions on what should be in the kids section.