Make sure the shed is big enough because you WILL get more! The best advice I can give is to build a LARGE chicken "run" around that shed so your chickens will be safe from all predators. Good luck.
The type of sand to use is called "washed construction-grade" and found at quarries. Check to see if you have one of these in your area. It a place where they pull sand and gravel from the gound and sell by the truck load!
I use the construction-grade sand that you can get from a place where they pull it out of the ground and sell it by the truckload. Check to see if you have a place like this in your area. Contractors get their supplies of soil and gravel from places like this.
I use sand in my coop so that it is easy to scoop with a kitty litter scooper. I have straw everywhere else as the chickens like it. When I cut the straps on a bale of straw, they spend the next week spreading it all around the run. I pull out any straw that is soiled from the nest boxes and add...
My understanding is that there are two types of calcium for the chicks. You want them to have both so you control their access by separating them. It is also advisable not to add the calcium to their feed because they can get too much and get sick.
The start looks great. My only comment would be to use hardware cloth around the bottom to keep out predators. Chicken wire is meant to keep chickens IN not predators OUT!