Mediation in a Separation

My stbx''s solictor has written informing me that she wishes to pursue a Deed of Separation. The letter also informs me that the (previously informally agreed, equal 50/50) childcare arrangements would be ''every other w/end + 1 night''.
Finally they suggest mediation or, if I am unwilling to mediate, then use solicitors and supplied a form E.

My question is this: I am of course willing to go to mediation. Does this mean that Form E does not need to be completed?
And even if it does, there seems little point in completing the ''Income Needs'' section, as it depends entirely on outcome of mediation regarding childcare.

Finally, does anyone have opinions on whether I can handle this self representing (with some assistance from the wonderful community here, or perhaps the Wikivorce service) or should I get other representation?

Is the mediation for the contact or to deal with the finances?

I think her solicitor is saying "here''s what she has decided is best for the children, now let''s mediate the finances"
As you can imagine, I''m far from happy with the arrangements, which need to be agreed first and foremost.

Any other thoughts on how best to respond appropriately?
Essentially, I want to say that I wish to go to meditation to discuss childcare (actually I''d like to discuss it with her in person, but she refuses to discuss it).
I''m very new to this, I assume my letter should be addressed to her solicitor rather than her?