Threesome help 😩

Recently I started seeing someone and it's been going extremely well. We have incredible chemistry, were friends for a while before, and he treats me like I'm the only girl in the world. We are also extremely sexually compatible. I happen to have a "sex bucket list," and a threesome is on it. He brought up that he'd be cool with it if I wanted, but said he would prefer a girl we know (one of my best friends) because he doesn't trust random people. Have any of you ever done this and how did it affect your relationship with either person? Or how do I convince him that someone random is better than a friend? I'm worried it will be awkward between all of us if it's a friend.