I did it! I put the kids outside with the flock yesterday. The first thing that happened was the rooster came over to check them out. The light chick (Barba) ran over and pecked him in the face. He pecked her back (gently) and she ran off, just to return 30 seconds later and she pecked him again. After that, the two pullets and the rooster went into the trees down the hill where I couldn't get a picture. Both pullets were pecking at the rooster's hackles until he got tired of them and ran back to the barn.
Eventually they came out of the trees, went to the back door of the house to eat some pebbles, and then made their way to the front door. I only left them out for an hour since I wasn't able to supervise them any longer. The cats helped babysit, too. Everyone had a great time.