BS(me) 46, Two wonderful teens.
So, when he brings up he wants to pick up at 8pm and drop off at 7, your only response is, "I do not see how that benefits the children." It's obvious he just wants that so he as the overnight without any of the work.
Let HIM sit there and try and justify how the kids being with you, having dinner, doing homework, and THEN him picking them up to drive half an hour to go to bed, then up earlier than normal in the morning to come back to you to get to school on time is GOOD for them.
He won't be able to justify it benefiting the kids, other than he wants it because it gives him another overnight against CS. You know it. He knows it. The mediator should know it.
Sit there, quietly. Let him try and explain it in a way it will make sense. See what the mediator says.
Your answer at the end is, for 5 years they have been at my house on school nights, and they are well adjusted, doing well in school, etc., etc. I do not see how this change would give them any more time to actually spend with dad, it would just screw up their sleep on a school night. Then, walk out if there isn't anything useful to say.
The plus of mediation, is you can ALWAYS say no. Also, if you are afraid you might get talked into something, you can say I will have to think about that, and end the discussion.
He is no longer my best friend. Repeat until it sticks.
WH says marriage is over: May 15, 2009.
EA#2 July 20, 2009. Legally sep: Aug 16, 2009. DIVORCED!!!! Signed Nov 23, final Dec 24, 2010, adultery listed.