kids' stuff

noun2

1. •
   (informal) Something done by, used by, or characteristic of immature people, especially children.

   • The scene on television is of a boy's bedroom. The camera pans slowly across ageless kid stuff: baseball cards, posters, clumps of dirty laundry. — 1993
2. •
   (informal) Something that is easy to do or easy to understand.

   • It's kid stuff to barrel along in a car like a big shot. I kept the needle right on fiftyfive. — 1949