DH attends court ordered mediation tomorrow. Any input on what should be expected? How does it work? Has anyone had success in this venture? Any do's and don'ts?

Very brief motion run down:
BM wants primary custody and care b/c of (false) allegations about me. She doesn't feel that EOW is in the best interest of the children. What she wants regarding split time is unclear.

DH was told by his attorney (who FINALLY returned his calls)that he could request his primary concern- immediate sale of house- as an uncompromising point. If BM will not agree then he can end mediation stating he is not willing to discuss anything else if she will not sale the house and feels no change is necessary.

Atty says that there isn't much he can do about the allegations unless they go to court and he can present evidence to contrary.

EOW just makes the most sense to us. Joint custody is best. She is only seeking primary custody/care in order to keep her kids away from me. Fine, but that is disruptive to our household.