Welcome to the Forum Maureen!  I apologize for not getting to this sooner.  Writing from the point-of-view of someone who has done extensive work with tactile diagrams, I would suggest that even at the age of 8 years, it is good to expose young readers to tactile graphics.  Something like a Venn diagram is usually fairly simple, however if it contains a large amount of text, you may have to use an alphabetic key, or possibly a simplified tactile graphic along with a transcriber's note explaining how the information is shown in braille.
Hope this helps.  If you require further assistance, I suggest that you could post an attachment of the print page with a question under the Tactile Graphics section of the Forum.
Betty