Oh you'll get them out in that beautiful new tractor you made soon! Seriously I'm jealous! It's perfect!
As for the sand, I had to try it. I hadn't raised meat birds since I was a kid, and really wanted to try and make it more than just 8 weeks for consuming food and laying around for them. I was floored at how much they play, run around, and dusted in that sand box. At 6 weeks old tomorrow, they still saunter out of the tractor and "bathe" in the nearby gardens. Granted they waddle...and they never travel far anymore, but they do seem quite content! I found 5 about 40 feet away from the tractor the other day..which was such a feat at this point, DS13 called me outside to see them trying to waddle up the hill... I can not imagine what possessed them to go so far, normally they stay within 20 feet of the tractor...they LOVE lying under the trees deep in the leaves that I *cough* "deliberately" didn't rake...just for them.