Slight tangent: My daughter's got heavily into children's MMORPGs Club Penguin and Bin Weevils and insists on playing them with me ('cos it's more fun that way). Small children, of course, are great to observe, because they show all the cognitive biases all at once, almost unmoderated. And the business model for these things is "addict the kid utterly so they nag their parents into buying a membership" (I am resisting), so they have to get it right. So I learn all sorts of things about user interactions and interface design.

Both these games have occasional quests (usually secret agent missions) in them, where the player has to solve a puzzle interactively, and what you're planning sounds like that sort of thing. Sooo, I suggest you find a child and play one of these games with them - look at the interaction, look at what the kids like, and look at the quests.