Forget for a minute the assignment and ask yourself this question:
"As an architect, your designed architecture could be implemented without ask you for more details ?"
The main thing of an architecture is to provide a way that developers could implement the system without any doubts. If you agree that this approach could be meet without more details in that use cases, so go ahead, do not create those diagrams.
That's is one thing that Sun is going to
test you ... you decision power!
Best Regards,