This is the standard function of a Google Ad Grant. You can absolutely create search ad campaigns that direct users to a specific landing page on your non-profit's website.
This is the most critical part where you need to be careful with Google Ad Grant policy. This is often called "gated content." While it is allowed, the primary purpose of your landing page cannot be solely for commercial or information-harvesting purposes. Your page must provide value beyond just the form.
This is the easiest part and is 100% compliant. Once the user submits their email address, you have two excellent options for delivering the video.
After the user clicks "Submit" on your form, you can configure the form's "thank you" action to automatically redirect them to the specific video URL on YouTube.
This is the recommended approach for the best user experience. After the user clicks "Submit," they are directed to a "thank you" page on your own website. On this page, you embed the YouTube video directly.