During retreat: to help with the dishes during meals before, during and after, set up and tear down after certain workshops, help coordinate people to attend the workshops, cleaning up
After retreat: clean up, moving items out of retreat
Additional needs: marketing, photography, promotion, organization, emails, follow ups as needed and depending on personal skill set
These are some suggested items and you would not be the only person helping on these projects but others would be there to help you too including myself.