Another crazy chicken lady building a new "coop"!

[SerendipityMama]

I began with chickens just last year. I got 1 Production Red, 2 Easter Eggers, 1 Black Sex Link, 4 Americaunas, and 4 bantams (one of which I found dead in the pen

). I also got 2 Pekin and 2 Ancona ducks

. As we grow a large vegetable garden, I knew I couldn't free range them. Instead we enclosed an 18'x25' area with 2x2 wire fencing, 5' high, covered with bird netting overhead. For the winter we enclosed 3 sides with greenhouse plastic, as well as the two coops that are inside. Of course, all my chickens decided to roost in one coop, so most had red rumps through the winter. (No mites, lice or anything.) Well, now Spring again and the chicken bug bit! I now have 23 chicks - Americauna, Cuckoo Marans, Silver Laced Wyandotte, 1 Easter Egger, a Red SexLink, Welsummers, Black Australorps, 2 Light Buff Brahmas, 2 Salmon Favorelles, 2 Speckled Sussex, 2 Dominiques, and 3 Polish Cresteds!! Also , 2 more Pekins, 2 Welsh Harlequins, 2 Fawn & White Runners, 3 Khaki Campbell ducks, and a pair of Toulouse geese!! So now we are going to build a real "coop"/shed. It will be 12'x14', 2 3' doors in the front, a window w screen on one side and a regular door with a screen on the other side, pole barn style, 8' in the back, 10' in the front, metals siding.
FINALLY, here's my question - I don't plan on putting a floor in the shed. In my current space I've used straw, which is now about a foot deep. I've been reading about people using sand - should I consider this? Oh, and the two areas will be connected with fencing, so it will be somewhere around 25x40

(And now as I finish this short story, my husband is trying to talk me into a wood floor.) Any help would be greatly appreciated - I'm trying to keep the costs down as much as possible! Thanks!