Well, I let the young 'uns out today. They're about 8 weeks old. Plenty old, but it's the first chance I've had to be home and observe to see what the dog would do. I opened the gate, then went in and checked the hen that had been on the nest since yesterday morning (fingers crossed, hoping for a broody, but she was off the nest and another one on it - will have to monitor that situation more closely). Chicks found the open gate immediately, wandered out a bit eating grass. I brought the dog over to see how he'd react. He's the reason I didn't let them out sooner. I just don't quite trust him 100%. I was going to say "yet", but at this point, I don't know if I ever will. Anyway, he glanced in their direction, but didn't really react. I gave him a quiet "Leave it" and he looked away, then wandered off. This shows some promise. I still don't think I'll leave them both out unsupervised for some time, though. If I have to go somewhere, he'll be kenneled, or they'll be in the run. (When I came to the house, he followed me up instead of trying to hang around with the chickens.)
Now, off to check that potential broody situation.... Wish me luck!