First of all I'd like to say I really like the look of the photos on that site as well.
Notice the low to medium contrast on images.
Even when there is a fair amount of contrast in the pictures, the shadows never reach pure black.
No blown out highlights either (they don't reach pure white either).
That's what give these high key photos their soft feel imho.
- - -
What I would do;
- When processing raw, blacks = 0, contrast = 0, switch curve to linear contrast
- Up the exposure a bit without blowing highlights much
- AND get highlight recovery to about 50 (this will bring back lost details in the highlights with overexposure if there are any)
Then in Photoshop;
- I'd add a curves adjustment layer and do this:
to open up the shadows a bit.
These steps should give you a good start.
For the next part I'd play around with color.
I hope these tips help,