Yes, you can totally skip the login invitations by turning off the notifications before uploading/adding the users. Once the uploading/adding process is complete you can turn the notifications on. However we would always recommend you to send us the user upload file and we will upload the users for you. You can disable the notifications from Setting --> Settings --> Notifications --> Disable

For sending the login invites in a bulk, please contact us on when to send it to the new users and we will do that for you. As an site admin you can only send login invites one by one.