With the hot sun on your pots, many plants will suffer from the heat of the soil. If I could, I would make a wooden box large enough to be able to fill it with your mix, then plant your plants in their pots, and sink your pots in the wooden box of mix. This will stabilize the pots soil temperature and also help with the frequency of watering. Al

I agree with Al. Some sort of double potting would be good. Maybe a wooden container filled with something airy & absorbent that you could wet a couple of times each day, so you could take advantage of the effects of evaporative cooling. Coarse bark would be good, very coarse perlite would also reflect some sun. Otherwise, shading the containers from sun will help a LOT to reduce passive solar gain, which is your real enemy in this venture. Airy soils, like the gritty mix, can also run as much as 20-30* cooler than darker, heavier soils because of their superior gas exchange & the added cooling it affords. Herbs will really LOVE it.

Al