I let my ex try and peg me and I let her piss on me. I only did these things because I felt like she had done a lot for me and it was only fair to let her do some things that she really wanted.
As for the pegging, it didn't work out well at all. That shit hurt! However, getting my ass licked felt good and it is visually very stimulating. She also stuck a finger and my ass. It felt like I was taking a dump. And since it felt like the good kind of dump, I enjoyed it.
A couple months later she wanted to pee on my again. I said you can do it if you give me a blowjob. Although, we never went through with it because she couldn't do it for various reasons.
So my advice, ask him if he'll take it up the ass in exchange for a bj.