Using a soft focus lens, or applying soft focus effect in post, and perhaps add "the orton effect" , and adjust the levels will get you close. It also looks like some images have flaring, so shoot without a hood. They also seem to have played around with the colours, but if you pull up the luminance to clipping at around 60% the green grass turns yellowish as in those pictures. So after doing that and applying soft focus or orton effect, you are in the ballpark.
OK, I tried my thesis on one of my own photos:
It confirms the ballpark, but revealed that you also have to know that you want to do this postprocessing when you take the photos, so you can control the relative brightness of things in your scene. In my photo the hand is better illuminated than the face, making the hand extra overexposed after the post processing. My shadows are deeper as well, so those need to be pulled up, or avoid them when you take the photo.