First of all, the run sounds good. A couple suggestions. Silkies don't fly much (at least, mine don't) so unless you are particularly tall and want to go inside, your run doesn't have to be that tall. Mine is maybe 4 feet tall. The walls can be wire mesh but for shelter from the weather, I'd make an actual little house they can go in. Silkies are very sensitive to wet and cold and do not do well in the rain. I'd suggest something like this:
Unless you live somewhere with very mild weather. Even then, you'll want to be careful. I live in Arizona and it almost never rains here, so mine just have a roof and part of the sides enclosed with wood, but when it does rain I cover my silkies' entire small coop with plastic tarps, and on the coldest winter nights they get a heat lamp as well.
Keeping them safe fro predators is definitely important, good job doing your research!
I don't like straw as bedding since it tends to get moldy. My silkies like cedar shavings. Dried leaves will also work (just be sure they really are dry, or they'll get moldy like the straw). Others probably have some different suggestions; try doing a search for bedding types on this website.
Colors of silkies -there are tons, but the most common seem to be white, black, and buff. Some also have what I call "face fluff" (beards), some don't. My pair are bearded white and bearded buff.
Here's a website I found:
http://hubpages.com/animals/Silkie-Chicken-Colors
"The American Bantam Association defines 6 standard colors: black, blue, buff, white, partridge, splash, and gray. Other colors that are also popular although not accepted as standard are: red, lavender, porcelain, and cuckoo."
Finally, I have never mail ordered chicks, so I can't give you advice there. Good luck! You've chosen a great breed! 
