This article explains how non-profit clients can collect donations independently of ticket sales.
There are a few options to collect donations successfully:
Price Levels
Create an event with a donation price level that is Pay What You Want.

Create an event with tiered donation prices as price levels or products (ex: $10, $25, $50, etc. as regular price levels/products).
Donations Feature
Important: Donations Eligibility
The Donations feature is intended for organizations that are legally permitted to collect charitable donations.
If your organization is not a registered nonprofit, your payment processor may restrict or prohibit the collection of donations through your account. In these cases, the Donations feature may not be available for use.
If you are a for-profit organization and wish to collect donations on behalf of a charity, please confirm with your payment processor that your account is authorized to do so before enabling this feature.
Use the Donations feature, found at the bottom of the Checkout step of the event build.

This will allow the customer to opt into whatever amount they choose, and will list the charity.
The seller will still have to pay their service fees based on their agreement. Donations are being sold as tickets, so the fees still apply.
Reporting
- Run an Order Report and add the donation column (which will total at the top of the report)
- Run a Financial Item report and group by Item Type to see total donations
For more information on reports, visit Report Configuration.