I recommend against a multi-tool, or a knife with more than one or two blades on it. As a learning event, the kid can best understand and appreciate what you keep simple. A locking blade would be preferable, and something with enough handle for his hand, but not too much so it becomes unwieldy. They don't need a big thick blade, but something slender and with a fairly fine point would help them learn blade control better I think. Case folders are special enough that the kid might have more respect for it than some $10 generic thing, and Case are well enough made that it will take some abuse.

I took great care of the little stockman that Grandad gave me. It was a great choice for me as a first knife. Grandad knew what he was doing.
The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer, English Philosopher (1820-1903)