Greetings,
You would need to contact Agilent to see if they have build DAQmx support for the VEE 6 Pro. As you mentioned, VEE 6 Pro makes DLL calls to the NI DAQ driver.
You are correct in that the M-Series boards are only supported in DAQmx. It is possible to use Traditional DAQ and DAQmx at the same time as long as you are using them on two different boards.
Hope this helps,
Anuj D.