PS. Remember this is for developers to understand the implications of things not everyday users, a developer needs to care about confirmations all the user and point of sale device need to know is did the money come in and the programming implemented into that point of sale device will decide when it is appropriate to accept this as true which is a programmers job.
Okay - think I'm understanding a little better what you are getting at and IMHO describing how a block is "added" to the blockchain is probably actually essential for a developer to understand the safety of the Bitcoin system (if you try to omit how Bitcoin protects against double-spends then you have omitted any chance of them understanding the security).
I don't think that finding a "nonce" that when hashed along with other information provides a value with "x" number of leading zeros is really very difficult to understand although I guess you could use "hashcash" as a simpler implementation of POW (I have some C++ source code for this if interested) that doesn't involve a "chain".