I thought about not posting because my experience is not about farm labor, but I think it still holds true for you.
I recently hired a couple for web development subcontracting for my web design business
Badgett Web Design. I'm currently running this business from Costa Rica while producing an
online permaculture design course. This is for my wife and I's permaculture education website
http://organiclifeguru.com.
Keep in mind I've hired a lot of independent contractors in my work of helping businesses get more leads and sales via the internet. I've also been a subcontractor myself for other agencies, so I have a lot of perspective.
With a couple you get two brains and more output (even if they have kids) in my experience. Their individual strengths also shine thorough so you get more creative thinking and problem solving on your tasks from their net strengths.
Hire them!
There's also a weird discrimination against couples and especially
unconventional families in the United States, so you have a unique role in being part of challenging whatever stereotypes are in place.