The below (which are best read in sequence) are mystery stories aimed towards younger children. Children of fifth grade or below will probably appreciate them most if the stories are read to them. Each story contains a wealth of detail; some of those details are clues which will be needed to solve the mystery at the end. If the children are struggling then feel free to re-read parts of the story or give them some extra clues before the story ends. By sixth grade or above the reader should be able to handle the text on their own. Even then slow, careful and even repeated reading may be required.
The stories are 'good clean fun' and tend to celebrate the triumph of good over evil. That said, they were initially written for a family of four boys, so there are one or two places that those of a more delicate disposition may consider 'gross'.
For those of you who are wondering; Pheidippides and Andromeda really exist (although they are a not quite as exciting as the stories suggest!)
If you have any feedback; especially regarding suitable age-range or anything your children liked or struggled with, please contact me at firstname.lastname@example.org