It's really cool website. But if you intend to use it to explain how Bitcoin works, pay attention to how the website illustrate blocchain.
The blockchain itself
Dispatched trucks park in a strict line down the road and are never reopened. Each new truck adds a ✓ to the ones behind it: a "confirmation". This is why Bitcoin cannot be rewritten.
This part alone feels awkward/weird to me, since actual mail is send to the receiver.
I like analogies but this one made me confused as a beginner. Letters are supposed to be delivered to the recipients, but from what I understand, there is no "delivery" in the blockchain because the record itself confirms the transfer.