Don, somehow I don't see you putting this group out in the yard. They are beautiful. Can you teach them to chase siblings? Or get the sibling to wear a bunny suit. 
You are soooo incredibly right. Greyhounds are not outside dogs. And they will let you know it. For a little while, when the weather is too they're liking, and they have a mind to, the outdoors is a wonderful place. But the inside with its soft surfaces and ready food and water is a muuuuch more wonderful place.
It would be so nice, however, if they could chase siblings (I've only got one). When they do chase and catch they are sooo good about bringing the capture right to the door and are so proud of what they've done. I can close my eyes and imagine the sibling, drunkenly grinning and hanging there in the big dog's jaws, just waiting to be dropped indoors. I'd toss her back outside and tell the dog to go play the game again!