I would tell the counselor before the session that that is your plan. I would certainly hope that they would be professional about it!
I sounds like you are being very thoughtful about how you are proceeding with your husband. That was also my approach and I will tell you that it has made a big difference on how we are able to get along well now.
I am trying to be thoughtful because I know divorce is not what he wants, but I feel so emotionally disconnected from him now and I know I do not want to carry on with the marriage. I feel like I am becoming the toxic one, not communicating with him and shutting down and I don’t want to carry on putting him through it, but it’s also because I know I need to tell him I want a divorce and it’s just so hard, so I’m shutting down completely