<ManagedAccounts>
   <ManagedAccount CommonName="svc1">
                <Username/>
                <Password/>
  </ManagedAccount>
  <ManagedAccount CommonName="svc2">
                <Username/>
                <Password/>
  </ManagedAccount>
</ManagedAccounts>
-----------------------
  - name: SP Service Account
    xml:
      path: "{{ xml_file_path }}"
      xpath: "//ManagedAccounts/ManagedAccount/"
      attribute: "CommonName"
      value: "svc1"
      add_children:
      - Username: "{{ 'abc' }}"
      - Password: "{{ 'def' }}"
----------------------

TASK [SP Service Account] ******************************************************************************************************************************
fatal: [localhost]: FAILED! => {"changed": false, "msg": "parameters are mutually exclusive: add_children, content, count, print_match, set_children, value"}