unfortunately I do not have experiences with the Upgrade. From a MWG perspective I would expect the migration be work without any issues. However I cannot promise. It sounds like there are multiple domain controllers available. If there is any chance I would recommend to take a test MWG installation, have it talk to one of the DCs scheduled for being upgraded and perform the upgrade. Afterwards see if MWG continues to work.
This would ensure a smooth upgrade. Maybe anyone else has more experience with this.