I noticed that a lot of apps for young children seem not to test them properly with real children. Examples:

- No / bad multitouch. Children will touch the screen when holding the device and then use the other hand to perform an action. With no multitouch or focus on the first touch action the app does not register later actions and the child gets super frustrated. In addition, with very small hands it is very likely that multiple fingers touch the screen, especially the thumb if the index finger is used.

- Controls close to the edge: On many devices swiping actions close to the edge will trigger phone status menus or switching between apps. This will confuse children.