Hi, Lindsay. Thanks for your interest in our plugin suite.
Your non-profit organization may be interested in our Do you offer discounts for nonprofit organizations? help article.
We do not have any demo of the wp-admin area to provide to you.
We use our easy-breezy Refund Policy (https://theeventscalendar.com/knowledgebase/refund-policy/) for such requests so you can buy one or many of our add-ons and thoroughly test them.
If you want to click around a demo of a site running our add-ons, please visit our front-end demo site at https://wpshindig.com/events/
It sounds like buying Event Aggregator (EA) and trying it out would be best for you. If you’d like, you can send me the Google Calendar .ics link and I can try it out for you and report back.