You are in a tough position. I feel for you. I am going to try to look at this from a tiny different perspectiv then the other posters.
JWs teach to turn their backs on non-JWs, completely turn. Others are watching you, and this could be your own children. I firmly believe that we reap what we sow. How you treat your parents is going to reflect on how you are treated in old age by your own. I am not trying to guilt you, but shunning is a learned behaviour (or, an excuse on how to act).
Your parents zealousness might be a result of another strong need. For me, both my parents were JWs. They were both severely abused in childhood. JWs offered an idealistic escape of the perfect life. For me to take that hope away from them, would be to destroy them. I see their JW involvement as a comfort.
That being said, I think now is the time for everyone to put their cards on the table. I think you and your wife have to first have a discussion (or two) about the situation. Does your parents know how you really feel about the WTS? I encourage you to tell them as gently as possible, and without breaking their own illusion of the Truth. If you kept this away from them, it would harm them should they move into your house. If you honestly tell them that you no longer support Jehovah's Organization, then they might decide it's best to not move into your house....rather than you barring them. Again, support your own viewpoint, set boundaries, and support their right to worship Jehovah by informing them that they would be living with someone who doesn't wholly support Jehovah's Organization.
The nuts and bolts of losing a job. To get unemployment benefits, your dad has to apply. In most states, you have to be actively looking for work. I've seen benefits be denied because the person said, "Oh, I'm taking a few weeks off" or "I was sick and couldn't look for work" or "I decided to go to school and work part time." What your dad tells unemployment could hurt him badly. He needs to read up on what to say. If your dad has physical or mental limitations that might prevent him from working, then he needs to get a doctor's evaluation as to whether or not he'd qualify for social security disability. It's easier to get the closer one is to retirement. He needs to apply for food stamp assistance, and whatever else the government offers in the meantime. He's paid for these benefits through his many years of working. Now, may also be the time to sell his house. Markets are up and banks are super willing to "short sale" a house especially if the breadwinner has lost his job and/or must get a job elsewhere. Talk to a real estate agent/attorney in your area. I would give him this information all under the guise of supporting his and your mom's right to independence.
Is there any different area your father could go in? How about working in a car parts shop? I know that one car parts shop was looking to sell a store, and offered to work with any potential new owner becuase the original franchisee had died. Something like this could be a great opportunity for your mom and dad. Again, support his independence by giving him ideas and alternatives.
It sounds like your mom has stunted her own growth. There are JW women who do participate outside the house. She hasn't had to do so for so long, and getting back into the workforce is super hard for these women. Perhaps your wife has some ideas on how to talk with her?
I don't know how much your familly can take on, financially and emotionally. Whatever you decide, you have to be upfront with your parents. And, they need to be upfront with you. I'm sure you don't want them living out of their car or going hungry. I knew a sister who did just that, becuase she was too proud to call her son who was no longer in the Truth. She tried to commit suicide, and went to the State mental hospital. But, if they do eventually move in with you, you are going to have to set firm boundaries.
Skeeter