I've been contemplating something similar myself, setting aside a pocketknife for my nephew and one for my niece, Logan is 6, and he's starting to get curious about my hobbies, knives and guns, Sage, 5, is also quite inquisitive, but more along the lines of "why is Logan interested in this, maybe I should be too...."
Logan's already learning to respect a sharp blade (and firearms), he knows my knives are kept atom-splitting sharp, and that he must be careful around them, I think what really drove the idea home is when I let him examine the edge of one of my knives under my Meade microscope at 100X magnification, seeing a mirror-polished edge at 100X really impressed him
He has a cheap plastic fake SAK that he's been using, but he knows it's fake (his parents got it for him), he was proudly showing me the saw and the two "blades", so I got out the SwissChamp I might be giving him (he doesn't now it's his) and we went through the toolset, his eyes got as big as saucers
"Wow!, that knife has *EVERYTHING!*, COOL!
Once I clear it with my sister, I'll present the knife to him, I'll slightly de-sharpen the blades, not too far, but I won't get them to atom-splitting until I know how he'll handle the knife, and I'm not going to round off the tip of the knife like the My First SAK, to me that says "here, you can have a knife, but I really don't trust you to not hurt yourself", it's better if he learns to respect the blade from the start, and that means a knife with a point
I like the baby carrot idea too, good way of safely explaining the element of risk that knife use carries....