I talked to my boyfriend about it last night. He said he'd want to finger her to get her all wet first. We'd both fuck her real hard and deep... and I'd get off on the idea that you're watching it happen.
I would jam my thick cock all the way in and then rough fuck fuck her (like the guy in this video), but I'd be sure to hold steady at max depth while I'm gushing my seed into her. And then my boyfriend (with a thicker dick) would do the same.