The first 3 qualifying stays between January 16 and April 15 will earn double points.
Is a cash + points stay a qualifying stay? Would this then be pertinent to the 'cash' portion?
I guess I've also never questioned if a cash + points stay would still earn points on the cash portion of the room rate - I always assumed it would, but that might be another variable.
Unfortunately, you will not earn points on the cash portion of a cash + points stay. It will also not count towards the MegaBonus. Here is a decent resource: