Hi Mitchell,
You have a handful of different options but I would use Shopify. https://www.shopify.com
A few other ideas for your online business:
– You can customize the text to ask for additional donations to your charity at check-out.
– You can offer Curbside Pickup and Local Delivery for contact-free shipping options.
– In the admin area, you can also pay bills and track expenses for your online business.
One more thing to think of, aside from the above, you could also list the calendars for sale on Amazon and Etsy.
Hope this helps,
Kim 🙂