night attacks make me think slugs, but the round holes sound like bugs. I would spray the plants with a little dish soap in a lot of water. The soap damages the bugs' exoskeletons, and probably makes the plants taste bad, too, but washes off when you harvest (or in a rain, may need to reapply).

is Makawao Ranch Acres on Oahu? I'm on the Big Island, near Hilo.

Thanks, steiconi,
Yeah, I think you're right; it means a lot of hand work ('cause I overplanted), but I sure want to save the little rascals.
I'll report back later.
Thanks again.

Look for little green worms (cabbage worm?), mine has the same issue and I found one today. Use BT.

Like the others said, probably either slugs or cabbage worms (or both). The cabbage worms are green and hide on the undersides of the leaves, so can be difficult to find. If you see those pure white butterfly/ moths fluttering around during the day, those are cabbage moths. They lay their eggs on your brassicas, resulting in cabbage worms (actually caterpillars).

I got busy with life awhile back and neglected my garden for a few months, and came back to find it infested with cabbage worms. I trimmed the plants back severely, removing all but a few leaves per plant (the outer leaves were half-eaten anyway) and then carefully searched the remaining leaves for the cabbage worms. Removing some leaves meant I had less leaves I had to search. I had to keep on top of it for a few weeks, because the adult moths kept laying eggs on my plants, but since I kept killing the larvae, eventually the existing adults died off and there were no new ones to replace them. If I had it to do again, I would just rip up all the brassicas and start over. The plants took a long time to recover, and I could have just started over and had nice, young tender leaves again from new plants. Your problem seems much less severe though, so I'd just do a good search for cabbage worms and deal with them before they become and infestation.

If you have slugs, Sluggo is supposed to be a good, organic solution. I have just started using it, and I think it is helping.