So, sitting out in the terrible heat proved worthwhile. To see the fruits of my labor (57 pictures, 27 of them usable and uploaded) simply visit my new Flickr Set: Wild Kittens.
I stayed quiet and as out of sight as possible by reading what Stephen Greenblatt has to say about Macbeth (just in case you were curious.) Apparently this did the trick because after a while the whole family (Little Grey Girl, the Fluffy Dark Kitten and the Calico Kitten) tumbled out of the tunnel. (LGG didn't really tumble.) LGG stood and let the kittens nurse for a minute, then went off in search of food. She never went real far, perhaps 30 feet away, but certainly left the kittens on their own, knowing full well that I was about 8 feet away. (I considered making a grab for them but I know that you're not supposed to catch cats that way, and besides, they were far closer to the tunnel than I was to them.)
At one point the Calico Kitten got very brave and started up the hill towards the sidewalk but a gust of wind blew a plastic bag at her, and she scurried back down. LGG returned to them within a few minutes, and they started playing with her tail and feet.
The kittens never get more than a foot away from the tunnel, and are clearly still nursing. I do not know how to lure them into a trap. But I want to catch them as soon as possible so that they can be tamed. ::crosses fingers::
Am off to the store-- I need more batteries for cat photographing. :)