Don’t be surprised if the coach makes your recruit an offer.
I assume this call is with the student. No need to come up with questions; you’ll want to know if there’s a deadline on the offer etc. But I’d expect the coach to volunteer that sort of thing.
Just be ready with a reply if there is an offer. “Oh wow, thank you so much! I plan on talking with my parents. Can they call you if they have questions? XYZ school is one of my top choices, so I’m very excited!” Or whatever script fits your situation.