I'd make sure that your coop is 20 ft. or more from the property line, and that's the surveyed line. Has there been a survey? If not, be conservative!
Your coop will be small, even at 4x6', during bad weather, and a run without solid roofing will be a snow covered mess that your birds won't want to walk on. I'd recommend building as large as possible!
One Silkie might be one too many; either get more, or none. They can be picked on by the 'normal' birds, so be ready for separate housing for Silkies if needed. They are cute, but may not mix well with the big girls!
Can you have roosters where you live? If not, have a plan for any that come your way.
Chickens are fun to have! Pick breeds that will do well in cold winters, and who aren't as likely to fly everywhere, because the neighbors won't want them in their yards, or in the road. Do you have a list already?
Mary