then use the migration assistant to move everything you want from the MacPro to the MBP.

It's not exactly a migration and you will need the Key to make the program work.

Best bet is to install Entourage on the MBP, bring it up to the same level as the MacPro and then move the
contents of the MS Entourage user folder, which contains the identities and the mailboxes, to the MBP.
Replace files and folders of the same name and, when you launch Entourage again, it will be just like it was on the MacPro