Dido,
You are still trying to dodge the bullet, and in doing so..you are setting yourself up to fail, and taking your H..your children, his W, and their children together with you.
Your lives are too intertwined with this family to cut ties with no explanation to your H. It will not happen.
You are very resistant to telling your H. It is not because telling him will hurt him..it is because telling him will hurt and embarass you . How do I know this? You are willing to continue to make him vulnerable to the destruction of his marriage rather than face the music. It is very telling and extremely transparent. If I am not fooled, neither will he be. The only realistic way to cut ties is to disclose..you simply can not get out of this one..sorry.
Once you have told your H..you two can decide together how to cut ties with regard to details and accountability. You really need this accountability. It is an important part of recovery for your M. If you want your M to truly recover from the state it is in..the state where you are infatuated and emotionally attached to another man... your H needs to have an active role..he can not do this unless you give him the information.
So let's put it this way, so that there is no misunderstanding...it is my opinion..that not only should you tell your H..you do not have the right to withhold this information from him..by doing so you are denying him the ability to make his life decisions with full and complete knowledge of the information at hand. You are denying him the ability to take preventative measures and to make improvements in the marriage. You are holding him in bondage to your fantasy and he has no choice but to sit and ignorantly wait to see if you decide to devastate him or cling to fidelity. This is wrong . It is cowardly. Please disclose.
.02 Noodle