The Skeeters are another story entirely! lol
The magnets work well. In conjunction with, or in place of the magnets, you could put bug zappers in the yards and or coops. this not only keeps the populations down, but offers a tasty treat, fresh cooked for your fowl.
There are plants that have some repellent properties but for the most part they do not really keep the buggers away unless topically applied, and even then they are not as potent as some might expect though they can certainly bring you, and possibly your poultry, some relief.
Here are a few plants that can provide some degree of relief.
http://www.gomestic.com/Gardening/Five-Plants-That-Repel-Mosquitoes.34525
Even better than a plant that repels mosquitoes is a plant that prevents their reproduction! These are plants that grow on the water's surface and grow so thickly that the mosquitoes are often either unable to reach the water's surface to lay their evil little eggs or are unable to emerge into the open air. The
Bladderwort will form a thick mat and even "eats" the larvae. There are of course others but I just can't remember the names right now.
You can do a search for such plants if you wish. They don't really grow that fast so it would be some time before the water plants become thick enough to be effective, but in the long term, if you live near the source, it would likely be a wise investment. Check with local regulations governing the introduction of aquatic plants.
Hope this helps,
Dave