It would be unlikely you would be required to pay a childminder as a separate part of maintenance
Maintenance is to pay for: clothing, food, childcare, rent or mortgage, shoes, etc. All the things a child needs on a daily ongoing basis. If your ex chooses to use any monies that you pay for your son on childcare then that is her choice. So many absent parents say that monies paid should not be going on so and so but it is my opinion that what ever the parent with care is using that money for is none of the absent parent's business (unless of course it is illegal or of detriment to the child).
I'm not sure what you mean by include payment for mother going to work? Do you mean can she use it pay her bus/train fare? then yes, of course she can because she is going to work to pay for things the child needs. Whether she uses the money she earns or the money you pay is is neither here nor there.
Maybe if you can be a little more specific please
What have you been told by the mother?