varying a contact order - confused!

[inthename]

hoping someone can help.
I've asked about this before, but now have the forms and it doesn't make sense!
ds is 12. contact order has been in place since 2007. ds has asked me if its possible to change it from next September as he knows he wouldn't be available at the times currently stated and doen't want it causing problems, so he wants to change those times just during school term times.
I've got the C100 form, but it says that you have to attend mediation first?
If thats the case, how do I sort out getting the order varied?
Also, can I write to ex with ds idea for revising the times and if so how do I write it (ex has history of causing world war 3 over such things)
and if he then agreed would this over ride the original order, or would something have to be lodged at court to prove that he has agreed?
When do I need to start this process and how long is it likely to take? Do I need to get a solicitor to do this for me?
Sorry for the 101 questions, I thought I just filled in a form, paid the fee, court sorts it out, but the C100 form doesn't read like that at all.

My DSS mum avoided the requirement for mediation by completing a C2, rather than a C100. The fee is the same and forms more or less identical - it's just the C2 should be used if there are ongoing court proceedings; she quoted the case number from the original court case where the first order was issued.

The court accepted it - it caused a delay when it finally got to court as CAFCASS had not been notified of the case so hadn't done their initial checks. The court didn't order that they go to mediation though, and (eventually) issued a new order.

If you want to avoid mediation, that seems to be a loophole to use.