Hello Andrew,
the internal port-channels towards the two processors of the WISM will be LACP, no other way as far as I know.
Regarding QoS you can trust the frames received using:
Enter this command to configure the QoS trust for the interface as reported in the document you have linked:
wism module controller 1 qos-trust dscp
using LACP should be an advantage for some aspects
Hope to help
Giuseppe