Liz, it takes two to mediate. Just like it takes two to dance.
If you are the only one truly "present", it doesn't matter what you want. You can't tango with yourself.
So feel free to let go of the expectations, maybe give him 10 days to get the refinance done, then just move on to the next step if he can't get his act together for the mediation.
When I divorced my first husband, I wanted to have the perfect divorce. Until it occured to me that if we could accomplish the perfect divorce, we wouldn't have needed a divorce at all. This is about cutting your losses and moving on into the next era of your life. There will be costs, and expecting your expectations to be realized is probably the first loss.
So glad you are moved and can go home to your own peaceful place! That's quite an accomplishment, and a source of renewal for you and your son.
ShootingStar1