Wife wants to watch me be penetrated

So I've never been penetrated by anything more than the tip of a dainty girl's finger.

My wife wants to see me go from 0 to 100. She wants her bull to fully enter me and fuck me rough in front of her. She says it will be fine because we'll use a ton of lube.

Thing is, his cock is like a 8oz Red Bull can. Is this going to be super painful? Is it safe? Anything I can do to prepare? I have until Friday night.

Also the plan is no protection. he already busts raw in my wife so I assume it will be okay.