I have 7 acres (recently moved) and we where is the same situation, "where?" Of course climate should also be taken in to consideration as well as convenience and safety.
At first we talked about putting the chickens out in the field. It would be a great option, flat, visible, but at the moment its mostly bare. No trees for cover for shade, and i have no other animals to go out in the feild yet. My biggest fear was distance would result in neglect, that and the distance to the a feed shed and water source. At a minimum a water source should at least be a hose that easily reaches the coop. I could always build an attached food shed later, but there isn't anywhere out there to hook up a hose.
So the next option was on the hill... understand my house sits on a hill most of the acres of land is a nearly flat valley on the south side of the house. I wasnt as worried about heat as our summers are very hot 100+ for almost 2 months and winter though cold hardly get below 30 degrees for more then a few weeks. So protection from the sun and heat was more important. And a mostly flat area.
Without building a coop on my lawn or driveway, we opted for under a large oak on the north side of the house about 15-20 feet from the drive way. It's a bit of a slop down to the coop and hubby will need to build stairs but the coop and run area about as level as we could get not being in the feild...
So for us under a tree for shade, close enough to the house that I can easily walk down 2 or more times a day and as flat and area as possible.
As for the garden, or in your case a further orchard. If you choose that area build the coop pick a spot that would have mimimal effect on the layout of the orchard. Off to one side or in a corner. Think about it this, close to the orchard could have is own benefits, free ranging in the orchard would help with bugs, some of the weeds and cleaning up some of the dropped fruits (if you plant fruit trees that is) also shade and cover from hawks. On the down side the birds might try to roost in the trees from time to time. Sorry i don't have a lot of negatives for the orchard.
For me my garden will go on the same side of the hill as my hens but will be fenced seperatly, partly becuase of deer and other animals but also so i can keep chickens out when I have seedlings sprouting. Yes chickens can be hard on gardens but in a well established garden with limited access that can be a really great help to.
What ever you decide make sure the distance is comfortable for you. Feeding, watering, letting the chickens out or just checking in on them from time to time. You want it close enough to be comfortable, but far enough that they aren't a bother too. As long as the coop is well ventilated and they have a shade area to get out of the sun the heat should be fine. And if its gets cold remember most chickens are better adapted for below freezing temps so long as the coop gets enough ventilation that it stays dry