If it is a once off task - I would do the registrations yourself manually.
If this is going to be an annual event you might like to take a look at the following modification.
ACP Add User MOD 1.0.0
phpBB: The All Important Rules - Bertie Bear 3.0 - No support via PM system - use the forums please.
phpBB v2: Retirement (1/1/2009) : phpBB v3: Read Me Topic - Custom BBCodes - Support Template
Matthew 7:7"Ask and it will be given to you; seek and you will find; knock and a door will be opened to you."
My Links: MS MVP (Consumer Security) - Malware Removal:University - Own Forum: Custom BBCode testing