I've been an NRA basic pistol instructor for a few years for adults and now I want to expand into teaching youths and need some tips.  I plan on starting with 13 to 17 year olds, then teach younger children.  I haven't gave any type of classes to children before so need help on general teaching tips for kids, how to explain firearms concepts, and special equipment or training aids I may need.

Become a NRA coach.

They already make a book for explaining firearms for 10-12 year old reading levels.  The Hunting Education Syllabus for the majority of states use the same book.  Granted all the hunting related stuff are irrelevant for your purpose but the books cover how firearms work and what basic kinds are out there.  Go call your state's wildlife office and talk to whatever they call the agency's hunter education coordinator.  They should be able to drop you a free copy of the book in the mail so you can review it and see if it's suitable.  

As far as a ready made canned presentation, the NRA probably has already done it.   I don't know, I'm a hunter ed instructor but not an NRA instructor.  Unfortunately NYS has for a long time kept a double arms distance from the NRA.

I'll try that hunters ed book and see if I can use any of it for my class.  If anything I'll read it and it'll help me explain stuff better to kids.

I was looking into the NRA Coach but unfortunately I haven't seen one offered here in Hawaii.  I may take it on the mainland in the future.