display of a computer with all parts on display on a wooden board.
I'm not sure from your post if you have already decided the "text" (written or spoken) for each of the parts to be on display. If not, that would be my starting point in order to crystallize your requirement.
I'm also unsure what exactly you have in mind as the "display of a computer" because an Arduino isn't really like a PC or laptop and I'm not sure how good it would be for explaining, visually, what is in a PC.
On the other hand if you want to explain all the parts of a small microcontroller project then an Arduino is ideal.
However I suspect the kids might be more attracted to a project (or two) that shows some "cool" stuff you can do with a microcontroller than to a display of its parts. My inclination would be to make something "cool" and have story-boards to explain the parts and the concepts for the kids that are interested in that stuff.
Another option might be to have the text (or spoken word) display on a PC that is connected to the Arduino. Probably a lot more flexible (and cheaper) than making sound snippets come from the Arduino.