It's kind of a catch 22.
I was the tech guy so I would import the CSV files to MailChimp.
If it came to actually edit records, our secretary-type would open up Excel, edit, then send it to me as a CSV. I'd then just re-upload and tell MailChimp to update changed records, and ignore duplicates.
If you made the site show that it's Excel editing in real-time that would be more convincing and less intimidating to the Secretary-type.