I appreciate the feedback from everyone.
I am not present when the cats come around because that scares them away, so the advice about using a string to selectively close the trap won't work so well for me. The good news is that these "kittens" are almost a year old, so we don't need to worry about mom's interference. If I caught the wrong cat, I'd just take him/her to get neutered, then try for the injured one. I'm using tuna for bait, but I will get some sardines packed in oil - what a great idea!
The raccoon I caught was a young one - not really a baby, and definitely appeared to be self-sufficient. It actually was larger than any of my dogs (Cavalier King Charles Spaniels), so I wasn't worried about it being too young.
Anyway, I haven't caught anything in the trap since the raccoon. Strangely though, the food was gone this morning. I have NO clue how the trap didn't close!
I'm going to keep trying to get the injured cat. The leg is looking really bad...the paw is terribly swollen and the back of the leg is black. When the cat is close enough, it smells like a rotting carcass. It's still eating, stalking prey, and getting around OK, though. Please keep your fingers crossed.