I don't have any novel ideas for how to get agreement. I brought it up right after a particularly painful argument when both of us were thinking, "tomorrow, I call a lawyer." I just said "I heard of a program that is supposed to help people like us. It's called Retrouvaille. I think we should try it." He said OK.
Others have pointed out that it helps the couple with communication, which is needed either way the marriage goes. Some have suggested it will help resolve their unsettled feelings. Some people have made the point that they refuse to continue living in the status quo -- either Retrouvaille or divorce mediation, but no more living together unhappily.
And of course, many do it because both parents agree it is the best thing for the children if they can get along.
It is not a weekend of sitting and listening to lectures. You do listen to the leaders tell their stories, but they are broken into relatively small time segments. Most of the weekend is spent on the writing and discussing, just between the two spouses. My husband took runs in the evenings to workout, and I did yoga in the room between sessions. It is not just sitting in a chair. On Saturday afternoon, we all had a break to just stroll the grounds of the Abbey where our weekend was held.