Every puddle duck decoys to mallard decoys. period.
If you're going to hunt sea ducks then get to different set ups and have both ready to go depending on your choice for the day.
I would go buy yourself another dozen mallards, standard or mags, doesn't really matter. If you want to mix in a few "others", find a buddy or two willing to split a dozen widgeon or a few pintails. Or just buy them yourself and use only the bull pintails or drake widgeon to help and some color to your spread. No sense in lugging hen pinnies or widgeon dekes just for the effect of shear numbers. A nice puddler spread of 16-18 mallards, 3 or 4 bull pinnies and a couple male widge would look just fine.