Thank you for your question
My name is Clare
I shall do my best to help you but I need some further information first
Do children A B and D still spend equal time with each of you?
At this stage send them the information that they have requested - and a copy of the original Order.
Given the problems it seems that the arrangements do need to be revisited with a view to ensuring that the children are able to continue their activities - and to sort out the Child Benefit once and for all
The starting point is to try and discuss matters with her using Family mediation - but if that fails then you will have to consider applying to the court for a new Child Arrangement Order.
With regard to the specific questions you ask
1. Yes the CMS can override the Order
2.They could but I do not think they will
Please ask if you need further details