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.