Member accounts

Hi

We have a multisite installation. We are running fairly big projects inviting up to 3000 bloggers to a specific site in the network. So whats the best way to handle this?

A few ideas

Create some kind of registration page (mayby using https://premium.wpmudev.org/project/membership) and send out a signup code (https://premium.wpmudev.org/project/signup-code) to the to 3000 bloggers. Is it possible to set which site the users are added to from the registration page?

What happens if the user is already registred. Will she be added to the site anyway?

Regards

martin