Has your husband considered getting allergy shots? Many people go to an Allergist and receive a series of shots for cat allergies, lots of times with good effect. Something you and your hubby should look into.
Have you ever heard of a product called Allerpet-C? It's a liquid you wipe on your cat's fur. People who are allergic to cats are allergic to their dander. This stuff does something to their dander, to help. I tried this years ago, for my brother inlaw who's very allergic and it made a huge difference. Here's the main page:http://www.allerpet.com/
Here's the page specifically related to the product for those w/ cat allergies (Allerpet/C):http://www.allerpet.com/products/product3.htm
Here's where to buy it: http://www.allerpet.com/sources/suppliers_a.html
It says that finer pet stores in Canada & the U.S. may carry it, also. For some reason when I bought it years ago, I thought I got it at PetsMart (Canada) but I could be wrong. Try calling around to see if you can find it locally.
Growing up I developed severe cat allergies, so bad that if I were to talk into a home with a cat and touch ANYTHING a cat (or cat hair) had been in contact with, I'd get hives on my face, I'd cough, be wheezy, itchy eyes, sneezing. But when I was 25 I decided I had to have a cat and I was hopeful that if I lived on anti-histamines for a while, maybe I'd build up an immunity. Chlortripolon Non Drowsy was what I took. I dealt with the itchy water eyes for a couple of months but I endured LOL. I now have 5 cats...including my first, the one I had when I was trying to deal with the allergies (16 yrs ago).
Do you live in a house or apartment?
Is there anyway you could at least keep the cats on one level of your home?
Be sure to always keep them out of your bedroom.................always. And keep all bedding washed well. A person with allergies needs to have one room in the house where nothing will bother them.
I'd sure try looking at all other options before making them 'outside cats.' the idea of a cat enclosure is great (for warmer months). As you know, in terms of just letting them roam loose outside, yes - there are lots of dangers that's for sure.