How to tell the doctor you want 2 embryos transferred?

All you can do is ask,and the way you've explained it in here would be a fine way to ask him. The worst that will happen is that they'll say no,and that seems unlikely to me because well they try to transfer many at a time,and twins is usually how they end up. He'll probably be ok with it,all you can do is ask him about it,again,the worst that could happen is he'll say no.