I use fans also. As for what else to do, it depends on how much work and money you are willing to spend, which is something with which we all struggle to keep a balance.
Providing a large floor or patio tile on which they can lie is cost effective and easy. Many people provide frozen plastic bottles against which the rabbits can lie; it is cheap but a daily task.
Real downside I see is that your property lacks shade from trees which would be cooling for the surrounding property, but that is not a quick solution on your land so I am thinking something like sail shades or screens and possibly misters. Shade to keep sunlight from heating the surroundings would help reduce the reflected heat.
Some people also use cement, plaster board, and the like to create a cooler environment. Foam board is a great insulator, lightweight and cheap. It should be used in the roofing of all rabbits cages housed in direct sunlight, imo.
If you really want to go for it...earthen sheds, sod houses, and the like are also quite cool inside even in the summer sun, should you really want to build something more permanent that will drop the temperatures for your rabbits and regulate tempertures in the winter. I am not sure how practical such things would be, but no rabbit would have heat stroke in them. Just saying....
The importance of shade cannot be over-stressed. Even partial shade is cooler than a structure in full sun, as urban planners have been learning for decades. If you can't build in the shade, insulating the roof will help - you'd be amazed how hot a metal roof gets, and a lot of that heat radiates right down to the rabbits.
I have seen people use sprinklers on the roof to help cool things off; my take on that has been a soaker hose (of course, my rabbitry is a bit larger than yours). A little evaporation goes a long way toward cooling things down; when the temperature is 95°, the coolest place outside is in my rabbitry.
My rabbit shed wasn't built as a rabbit shed, nor was it built in the shade, and you can feel the difference. All the things mentioned above I use except the misters. One thing I use that works awesome is empty 2Liter bottles with water, frozen and allow room for expansion. I have two sets. One is freezing while one is in use. The rabbits lie next to them and cool down a lot. It has saved mine in 100deg heat multiple times.
Great ideas. Thanks y'all! I've also thought of building a fence or some sort of wall in front of the hutch. It faces east so that would help with the before noon sun