Hello @AndrewF677 ,
Donations are an option available for those declining the event, but otherwise I'd recommend including links to where your users can make donation on your landing page (such as PayPal for example). Another option would be to include set donation amounts as items the registrants can purchase as part of their registration (standard processing fees apply).
As far as a freefom section to write-out things, this is available for both the person(s) working on the event form, as well as registrants to a degree. I'd recommend checking out this article on setting up custom question / block elements for your registration form.
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