I'd procrastinate, avoid and lie so you don't go with him - assuming you can't speed up the leaving plan.
I went to Relate and persuaded stbxh to do joint sessions to. Biggest mistake ever. He smarmed his way round her and it was a very effective new way to abuse me. The counsellor was rubbish and went all giggly and flattered in his presence.
She told me I was being selfish about sex and was withholding sex as a power thing. I should enjoy it for his sake and if I rejected any sex then I was rejecting the whole of our marriage.
It took me years of mumsnet before I realised that it's ok not to want sex when you're being repeatedly raped and left bleeding and sobbing each time.
That's how much couples counselling can screw with your head, im quite bright usually (!). But stayed with him and sacrificed everything for him, to try and keep him happy. And he got free rein to carry on the shocking levels of financial, social, emotional and physical abuse, and of course the sexual abuse. It was only when I could see DS was being damaged that I found my courage and got us out of that terrible situation. Had no idea it was as bad as it really was at the time, as I thought I deserved it all and it was all my fault. I even thought I had the anger problem, not him, and spent my life apologizing and trying to be better... obviously my anger problem was the reason we had fights, ahich were the reason he'd get angry which was the reason he 'lost it' and abused me. Yup clearly my fault. Err, not that I was crying out trying to live with the intolerable strain of being abused, and that it's ok to be unhappy and not coping in a situation that no one would be able to cope in. The trick is to change the situation though, by walking away from the person causing the hell, rather than living in endless hell trying to make it ok by making him ok.
Breaking away is tough, but it will be the best thing you ever do. And also, breaking away is nothing compared with living with it, really!
Maybe if you went into it with your eyes open and there was a massive advantage to you to go through a single session.... but no, I can't even say that, being in an abusive relationship messes with your mind so much I think you're terribly vulnerable and shouldn't risk it. It's handing him a whole new way to control you, to hurt you, and cut off your escape routes by making the outside world believe you're the bad guy/ the loony / shouldn't be believed. And quite frankly, he's got enough ways to do that already!
Good luck, and keep your eyes on the prize (as it were!). You, without him. Healing and learning how to live again.
It's a good world out there if you can avoid the sharks, and you deserve to be able to experience that beauty and joy of just being alive... Kinda hard to do that from inside a prison isn't it? 