Tracy, you can get the SnuggleSafe Microdiscs from www.drsfostersmith.com
. I've been using them for several weeks now, and the cats have been fine with them. I was afraid that they might not use their shelters with an "unknown object" slipped under the straw, but there's been no problem. It's a great thing to be able to bring warmth to them now with these super-low temps.
Though it's very helpful that you've got a shed for the cats, it's a good idea to put small shelters for the cats inside it. The smaller the shelter, the less the warmth from the cats dissipates. Having small shelters within the shed to curl up in will keep the cats very toasty, especially if you use the SnuggleSafe discs. You can make shelters from styrofoam coolers, or even cardboard boxes. Small, wooden doghouses are ok too. For ideas on homemade ones look at www.neighborhoodcats.org/info/wintershelter.htm
Make sure you put a thick layer of straw inside each shelter, too.
It's sad that some of your ferals disappeared. This happened to two of my females. It's three years later and I still miss them and wonder what happened. Were your two mom cats and kitten already spayed/neutered when they disappeared?
It sounds like your original colony is growing with the other cats who are now showing up for meals. What's their S/N status? You don't want a feline overpopulation explosion in your backyard, so now's the time to trap any kitties still in need of neutering! Your original cats must be very easy-going to tolerate these "visiting" cats!
You mentioned socializing 5 kittens - how did that work out? Were they all adopted or did you keep any?
You're doing a great job for someone who's new to caring for a feral colony! Your hubby sounds like a sweet guy to keep trying to get the cats to warm up to him! If it'll make him feel any better, tell him most ferals react this way to men. Ferals usually respond better to women's voices, so tell him to try talking to the cats in a softer, higher voice next time - it probably won't make a difference, but at least you'll get a good laugh out of it!
Let us know how it's going - hopefully, the cats will soon be over their colds.