user import and initial login flow

Here is the flow I want to create:

– Import a set of users
– import other information about the user for user listing in BusinessDirectory
– Once both are imported, I want to select a set of users and send them an activiation email allowing them to login to their newly created account

Questions:
– Clicking on the activation takes them to a login screen, but how are they supposed to know their password?
– I can’t see where/how UM sends the username/password to the user, in fact, I’m pretty sure I read that you don’t do this for security reasons, so how is the user supposed to know their login information??
– Is there a way to do this?
– Is there a way to force a new password on first loging?

Thanks.

-Dan