The Carson LED pocket microscope is, for the money (less than $14), the single-best science tool I’ve purchased (available on Amazon—paid link). After using a clunky old microscope with a mirror, the new microscope is a dream. I popped in a AA battery to power the light and immediately got great results. It “only” offers 120x magnification, but for kid use it’s perfect. Plus it’s cheap enough that I won’t worry about it getting broken, so it will be great for backyard and camping use.
Just using a standard iPhone I took some pretty-good photos of a leaf, a feather, and a pen mark on paper: