A very interesting conversation for me with lots of inspiration. I'm at the Spanish Mediterranean coast, too! I'm in Mediterranean climate but it's less hot than in Malaga...
I think one of the most important tasks you have is protecting the soil you have right now. A friend of mine recommended having at least 10 cm (!) of mulchon my soil. It's great you said you can probably get branches that have been cut during pruning, see if you can get more of that kind of material.
In Portugal, I got chipped wood from the municipality because they saw it as waste material. Add some horse manure and hay from an equestrian centre and it'll be even better (you can get tons of that for free if you know the right places; the bigger issue might be being able to transport it).
I'd assume that many of the plants initially need to be sheltered from direct sun and protected from the wind. Two ideas directly pop up: 1) a heap of stones (the interior ones won't heat up much), 2) using corrugated cardboard (insulates well, doesn't let any sun through. You can build a shelter in a way they only get direct sun for a part of the day).
The cardboard you can also lay on the ground and poke holes for seedlings. Secure it with stones. The soil will stay rather cool and won't be dried by the wind either. With time it will decompose.
I know these thoughts are not what you initially asked for but based on what I read it could be useful for you and others following this conversation.
