Cool climate greens and companion planting

It's nearly June, and it's FINALLY time to move our plants outside of the greenhouse here in central Montana. We have a few planting areas around our property (we're renting so we still have to mow), but the largest area is in a partially shaded large low lying plot that tends to hold onto moisture and stay a bit cooler than the rest of the yard.

We've had issues in the past with things going to seed prematurely and drying out, so we're putting all of our cool-loving plants in here that may be more sensitive to the intense high altitude sunlight.

Right now we have chard, kale, broccoli, arugula, mustard, spinach, cilantro, parsley that we intend to put in that area. True to the ideas of permaculture, we obviously don't want to create rows and segregate the various plants, but instead intend to plant them all mixed in together.

Again, because we rent, we can't put in a hugelkultur bed, so these plants will just be dug into the ground and mulched.

My question is, should there be some method to the madness? Is there some companion planting/polyculture-y way we should set this up?