Getting back to the original tenet of your question, are you concerned that if you do offer up 'full and frank disclosure' on the finances that the mediation process may encourage your ex to look for a bigger share of the pot that the 50:50 you think you have agreed upon?
If so I would have to suggest, the mediator will not be able to proceed without all the financial information and if you end up in court doing it through sols - you will still have to give the info.
You seem to suggest theres been some periods of being amicable between you and ex interspersed with the flash points that we all know and love. If you can, try not to make any of the contested issues become your Bête noir if you have broadly got agreement on the main stuff. It isnt easy when theres a new partner in the background winding things up and you are indeed correct, the children might end up living with you and will you be receiving any financial support from their mother if this happens?
Perhaps it would be worth you posting the finance issues and checking with the more skilled financial posters on the forum, what is the worse case scenario - perhaps then you can work out if theres any way round that. Unless you are self employed its pretty difficult to conceal financial details however there are ways people do frustrate the process - it would be against my greater principles to expand on those. I think your best bet sits with maintaining a functional, reasonable and relfective realtionship with the ex to see if you can agree things. My ex husband and I did the whole disclosure thing at mediation we each were 'entitled' to things being split a certain way but we in fact altered that to suit our own thinking - and we were by no means in a good place, just a real one.
Thanks for your kind comments sillywoman and rasher .I have over the past 15months arranged my finances so that I am no longer in debt with the bank, it's probably the first time in my married life that they have been that way ! I was concerned however that this would be seen by my ex, as me holding money back from her, even though I was still paying the full mortgage and bills, since we split. I have had a fair bit of overtime which has meant working 7 days a week, but it has really helped. She will see this and naturally want more, then when it all stops, I'm sure will still want more ! Just yesterday my comapny announced 3000 more redudancies, according to a Sunday newspaper, whether this will affect us is unsure.
I had calmed down over the weekend and was trying to construct my finances around my soon to be transfered and increased mortgage. This would then enable a decent offer for maintenance to my ex, which not only covers my son but also my daughter, however I have just received an email from my ex, telling me that she won't be going to mediation again as it was too upsetting for her on Friday, also stating that she is going to claim maintenence through the CSA. So it's one step forward too many steps backwards !
So now we have to go through the whole thing again but this time through the sols.I think she just needs time out, maybe too much is going on, with her moving in with a new partner and leaving the marital home ? I know it's easy for me to become niggly over the maintenance issue and I do need to take stock of the bigger picture and all our futures.