Spouse visa extension documents.

Hi, I am currently completing the on line spouse extension visa for my wife. Non eu 5 year route.
I am a British citizen and my wife non EU.
I was married before to a British citizen and we had to 2 children.
When completing the form they are asking for evidence of my children. Birth certificate, proof of where the children live, evidence of parental relationship with my children and arrangement order between me and my ex wife, for my new wife to see the children.
The problem is I do not speak to my ex wife and getting these would be very difficult. she would never give me proof of where the children live. (Electric bill)
Do I need these? Any ideas??

Thanks Ross