kid's stuff

Noun

kid stuff (uncountable)

1. (US, 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 December 16, Patricia Davis, “Does Johnny Have a Gun?”, in Washington Post, retrieved 28 Jun 2017
2. (US, 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 January, John D. MacDonald, "Three's a Shroud" in New Detective (republished as "Verdict" in More Good Old Stuff, 2014)