How do I simplify multiple contributions?
This can be done with Webform-CiviCRM integration, and probably with Caldera Form as well.  You can create multiple contats on a single form, specify a single fee, create relationships between the organization and individual.  The annual reminder can be sent out in a number of ways; if you're using Drupal, I'd just use the Webform email functionality to send the email to all the individuals.