Andrew -- such gorgeous dogs! I've always loved Samoyeds, and yours look beautiful and sweet-natured (sitting nicely while you photograph them instead of licking the camera lens like mine do).
Mostly I used the Selective Color layer adjustment to reduce the magenta and the cyan from the whites. I reduced the magenta from the reds. I reduced both the magenta and the yellow a bit from the neutrals while I reduced the black a bit more than the magenta or yellow. I then added an empty layer on top set to the Overlay blending mode and used a white brush to lighten their coats and eyes a bit more.
I'm sure others will have other strategies to show you also. Hope these help you make a treasured keepsake.
P.S. -- looks like I blew out the whites a bit; Cyber Cat's fur shows more detail.