I am looking for a good translation that doesn't sound too technical. I read the definition of "síntesis" and found the word "compendio" which has a definition which seems to match "overview" well, but I am unsure how common this word is used in everyday speech. I am really looking for a word that a grade school student would know. Any ideas? Do any other words come to mind?
It depends a lot on the context, but as you mention síntesis and compendio, a word that is commonly used and has similar meaning is resumen.
Other expressions to have in mind: panorama, introducción, introducción general, plan de la charla.