I did a 1-hour show-and-tell 2 years ago when #2 kid was in
5th grade. I took an old 8088-based PC in, and we demolished it.
We took the disk apart ot expose the platters, pulled the cards,
took chips out of sockets, and popped the chips apart to look
at the silicon wafers inside. The kids loved it. That type
of demolition really apeals to 5th graders. Of course, I
explained that this old computer was worthless because it
was ten years old. I got in a simple explanation of
exponential improvement, (Moore's Law), and I had the kids
extrapolate the curve for me. I also got in a good deal of
computer architecture. The teacher, and the kids, told me it
was the best parent presentation of the year.
Moral: you don't have to be a scientist to do this stuff.