Substitutions for butter and milk?

Yes, they certainly would. I often make dairy free cookies just that way. Some plant based butters seem to have a bit more water in them than butter, so to make sure the texture is right, I usually substitute half Spectrum organic non-hydrogenated shortening, by weight, for half the butter. Since I've never made this recipe with those substitutions, I cannot say exactly what the results would be, but I would not hesitate to proceed this way, based on my experience.

I hope this helps!

;o)