So Chris,
Your parents have your son 3 days a week presumably as your ex works full-time?
Do they have your son at their house? Could you not see him at their house instead?
My ex walked out of mediation because he didn't like it when the mediator asked him to listen to my view (that would have been a first).
I asked my ex to put a schedule of contact on the table to see what he was looking for (everything has always been on his terms) but he wasn't prepared to do this. I then put a schedule on the table taking into account his work rota (which in itself isn't easy as a 16 week rota). I offered the "norm" (I use this term losely), what equated to every other weekend, and an evening during the week and also time during the day to see our youngest 2 children who at the time were less than a year, and 2 yo.
He said it wasn't workable. This then forced him to put something forward and he now has 6 sundays for 7 hrs and 4 friday evenings for 2 hours in a 16 week period. My children are 2, 3, 6, 10 & 12 years old.
If she really is unwilling to go to mediation I see little point, at least at the moment. Maybe you could put in writing what contact you would be happy with, even offering a gradual build up over time. If she doesn't respond at least you will be able to show her lack of willingness to come to any agreement.
Can I ask whether either of you have read a copy of the "Parenting Plan"? Below is a link for getting a copy of the Plan, it is a FREE publication.
http://www.tsoshop.co.uk/bookstore.asp?DI=586230&trackid=002289 Out of interest who was it that started the divorce?
Presuming that your ex works full-time, was this always the case or as a result of the seperation? Maybe she feels that she isn't getting enough time with your son.
I know all of these questions could be brought up at mediation and it is sad that she won't entertain it. I would maybe book another session and tell her when it is, providing her with a list of questions before you go maybe so that she can have thought about her response.
Sometimes, given time to reflect on things we see them differently.
I wonder whether as she is working that maybe if you suggested that one weekend you didn't have him at all but on another of the weekends that you either had him all day one day, or say 4 hours both Saturday and Sunday to give her a break, even if that was to just catch up on the every day things.
Having a young child you can feel like you have to be switched on 24/7. I never realised until I had that time what I was missing. Finding "me" again, even just for a couple of hours is a welcome thing.
xx Sarah xx