In a real team, you should not develop an entire architecture without help.
I can tell you how I had started my assignment. First, try to draw (by hand) some sequence diagrams for the operations. Forget about Web Customers and Java Application clients. Think only in represent the use cases in graphical form.
Get the BDM diagram and add some necessary classes (if you read carefully the use-cases you should come up with 2 or 3 new classes). Remember, this is the domain model. It is not necessary to represent intermediate components.
Start with Prepare Itinerary. Draw all the components and messagens (in plain english). It is better to draw by hand in this step.
When you finish all the sequence diagrams, it is time to think in distribution. Look at each component in the diagrams and think where must they be installed. Then try to create intermediate components, like Business Delegates, Service Locators etc. Try to map the remote components to EJBs or DAOs.