I broke down under the insistence of Panther Boy that one short evening walk in his harness was completely inadequate (and his siamese heritage is confirmed in the volume at which he tells me this) and purchased what the company calls a catery but which I've dubbed the cat coop. It's a wood and wire structure about 3' deep by 6' long by 6' high, positioned against the side of the house so they can go out the window into it.
Took quite a lot of assembly but with my trusty cordless electric screwdriver I finished putting it together today and it took the cats about 30 seconds to head out the window into it when I opened the screen for them. Little Calico surprised me by going first, closely followed by her brother. They practiced going in and out several times to reassure themselves they could get back in, then settled in for a long session of smelling and eating the grass and sitting on the perches checking out the yard from their new vantage, observed by the neighbors who had been following this odyssey with interest. They are now back in and asleep-- so much excitement seems to have tuckered them out.