We are excited to announce that we have launched our new Hive Community! HiveNation will remain as an archive, but all new posts, discussions, and articles will be created on Hive Community. You can visit our new community at thehivecommunity.aerohive.com
ID Manager allows you to bulk create the guest credentials, however, we do not allow you to bulk email them to the users. You would need to merge the credentials with the users and then use a mail merge program to distribute the credentials to the users.
We will consider this feature request for a future release, but will need to understand how to reduce the risk of being interpreted as a spamming mechanism.