OH my word, look at Josh! he's absolutely gorgeous, and I'd have him in a heartbeat if I was local! I too remember the pictures of him when he just looked like a mucky blob of fur, and now look at him so handsome and growing up so fast.
You are responsible for this and you should be so proud.
Perhaps you could say that prospective owners must be vetted, as in you need to go to the house (to check it out secretly) and have a chat with them, you could also perhaps print out informatin from the internet, about basic cat care, keeping the flea free, getting them neutered at the right age, benefits of neutering etc, and also give them your number so they can ring you with any problems or seeking advice, and if they ever have problems and cant' keep them, you'll have them back to find another home for them?
It sounds like a lot of hard work I know, but could be worth it, and perhaps if you husband helped it'd be something you could share and do togehter?