Small talk will take you far. They want to get to know your personality in addition to your qualifications. It's an all-hands-on-deck charity so talking to donors will inevitably come up in any position, even interns. But don't be intimidated. The donors are happy to interact with you. The organization wants people who can carry a conversation without pulling teeth. They want to see confidence.
For interns, make sure you're ready to talk about your studies, why you chose your major, and what you want to do with it. Be honest but keep your answers aligned with the organization's mission. All the candidates love sports, so find something else to talk about. Talk more about yourself as a professional and your future and why/how the internship would help shape your career path.
My interview process was one round on zoom. I interviewed with the COO, VP, an HR rep, and one lower level member of the team I'd be working on. I was offered the job by phone before receiving a written offer.