Even as an administrator having to add a single or very small number of contacts via CSV is painful.
So why not use the existing system email “Join the community” and allow it to be triggered through a very simple form that adds a single contact to that database and sends out the invite email on behalf of that user.
This promotes the organic growth of the community as people invite each other and might come in handy also in a B2B context to push colleagues to join.
Since you are tracking the referrer, you can also reward the behaviour and have a small referral program!