Which site....

You should discuss all three sites with your installer.
My biggest concern with site A would be safety.  In a worst case scenario with the wind out of the north and the tower toppling over towards the house, what would happen ?  The 17.5 kw Jacobs normally comes with a 26 foot propeller, so when you add 13 feet to the 100 foot tower, you may have a blade tip smashing down through the roof.  I would also consider the 1900 lb turbine breaking loose from the tower and bouncing at the house from 10 feet away. And lastly, when a rotating three bladed propeller hits the ground, it is not uncommon for an upper blade to snap off and get launched. A 13 foot propeller blade makes quite a missile. You need to consider these risks and determine whether they are acceptable to you. My personnal opinion would be, not within 150 feet of the house, and I would prefer 200 feet (horizontally, not measured up slope). So, on this basis alone, I would eliminate site A.
I would not apply this same standard to site B, because normally you don�t have people sleeping in the barn or shed.
For all 3 sites, you need to consider the rule of thumb that �nothing within 300 feet, comes within 30 feet of the blade tip in the lowest position�. For your 100 foot tower and a 26 foot blade, this would be 57 feet up the tower. You then �weigh� the amount of incursion, with the distance to each, and the prevailing winds to estimate the impact on production. It is as much an art as a science, so your installer can help you evaluate this.
Your Site B is not ideal with the 100 foot tower.  But if I followed your numbers correctly, a 130 foot tower at B would give you the same hub height as the 100 footer on site A.
I do not think a 130 is available from Jacobs.  A 120 is the biggest I�ve heard of. But what is the distance to the woods to the North ?  A 10 foot intrusion at 280 feet away is better than a 3 foot intrusion at 50-100 foot.  If you can �trade in� the 100 footer on a 120, this might be your best bet.  
Or, since they are in the non-prevailing wind direction, you might be able to go with the 100 footer and accept the �loss of production� with northerly winds.  Are the northerlies the same strength as the prevailing winds, or are they stronger ? There might not be an actual loss at all.
Site C.  My main concern here would be the trees at the fence line. Do they represent an incursion and how far away are they ?  Because this tree line is in the direction of the prevailing winds, it might be the largest impact of all three sites.
Oso