That's REALLY nice for a FREE building. What's your hubby putting in on the other side?
I would sprinkle down some Stall Dry or DE and mix it with the sand. The chickens will do a lot of scratching, so you don't have to worry about mixing too much.
I wouldn't use straw. It's not obsorbant at all. In the winter, I would put down wood pellets and aspin (or pine) shavings for a little more warmth.
Speaking of warmth - I wouldn't use a dowel as a roost either. The chicks would have to grip it all night. At the least, for full sized chickens, I would use a 2" x 4" with the wide side up so the birds can rest right down over their feet,
I'm currently using a left over piece of plywood that's 6" wide by 5' long for my eight.
They love to stretch out on it and have their whole underside resting on it. The down side is they get poo on it that I scrape with the kitty litter scoop every morning.
I'm considering switching to a 2 x 4.