Include him as in one of us play him? I don't think he would be surprised by it. Since he's got his injury, I doubt that he thinks Katniss will let him be a tribute again, and I'm pretty sure he's aware of her need to make him survive. I think he would feel a little guilty for Haymitch volunteering, because he's also probably aware that he should have and would have died if it weren't for Katniss. I think he'll be a fine mentor, though, especially since we're not including the romance between him and Katniss, and he can just help his friends out from the Capitol.