The daily test of emotional fortitude

[MLCxH]

IMHO, identify a list of mediators acceptable to you first.

"I would like us to select a mediator Here is a shortlist of mediators, if you prefer someone else let me know. and If we cannot come to an agreement and start mediation by date XYZ, I intend to file for D."

Note that stating you intend to file for D means that you should be ready and willing to do it if it comes down to it. I would say that only if you are firm and convinced about taking that step. If not, change the wording