This has been done at least two or three times before with books. What the heck, it's his money, and if he wants to have fun with it, let him. If people do find these tokens, at least some of the wealth will be spread around.
But I wouldn't call it an American idea. This same kind of thing is one of the most popular worldwide sports right now. Who doesn't like a contest? Who doesn't like unraveling a mystery? Who doesn't like the quest for buried treasure? Who wouldn't like to find one or two of thsoe tekens and swap it for a bejeweled treasure?
I can think of many worse ways he could spend his money, and tracking down those tokens has to be more fun than another weekend watching TV/
Millions do this sort of thing every day, even when the prize is a bauble you aren't allowed to keep.