A good way to jump start the project is to do something specific with the OS. Windows CE comes with a custom version called CEPC, which is designed to execute on an IBM-compatible PC. This is an excellent opportunity to get your team to start working with Windows CE before the target hardware arrives. All you need to do is dig up some 486 or Pentium-class machines.
CEPC contains a Boot loader to load the CE from DOS. The source code for this Boot loader is available with Platform Builder. This is one of the first modules that will need to be ported when the target hardware is available. Since it is so critical, the Boot loader should be extensively studied in the CEPC.
Next, focus on the keyboard and mouse drivers. A good understanding of CE device drivers will be gained through a study of these drivers on the CEPC.
CEPC contains drivers for a selection of networking cards. Another assignment is to purchase such a card, install it, and get it working on the CEPC. Adding networking capability to Windows CE is an excellent learning exercise in how to customize the OS.