Hello there
I hope you have managed to speak to a mediator by now and that you feel reassured. People are sent off to mediate these days with little thought given to what a scary prospect that can be. Sometimes there are clear power imbalances and if you've been a stay-at-home parent whilst your partner has been out in the cut-and-thrust of the 'paid-for' working world, it can feel like you are at a disadvantage (and quite frankly - irrespective of the skill of the mediator - you are).
I am a Family Consultant and help people prepare for mediation. I coach 4 key skills you need in order to make mediation work for you. You can find some info on those skills here: (I really hope its useful and you can use it in your mediation)
http://www.familychangeportal.co.uk/pre ... n-coaching
Please get in touch if some telephone coaching or a face to face prep session would be of benefit. You may want to consider a parenting plan - there are some templates on the website too.
Good luck.