I am married and have 3 kids (9, 7, and 5) and I have a very strong desire to thru-hike some day. From my perspective, I wouldn't do anything like that without them. I think that our tendency when we first get married or first have kids is to think that our "life" as we know it will end and all of the adventure will be gone, and that somehow the two (family and adventure) are mutually exclusive. This is exasperated by the fact that the media and outdoor companies portray an adventure lifestyle as only belonging to the young, single, just-out-of-college crowd.
Over the years I have consciously decided to try and reject that mentality and work towards having adventure in my life. I love my wife and kids, I love spending time with them, who better to share the world with than my family. Kids love adventure, being outside, getting dirty, having fun, and are way more capable than what we are typically willing to give them credit for. Spouse's on the other hand, may or may not be as receptive to those kinds of things. My wife has come a long way, she is now starting to catch the bug and is really enjoying getting outdoors. She wants to hike, backpack, and (since dropping the thought a couple of weeks ago) is now considering the concept of doing a thru-hike one day! This is quite an achievement coming from a girl who never spent one night in a tent while growing up.
I think the key to achieving goals like this is time and creativity. Start small with your wife and kids. Try to do day-hikes regularly, starting with short walks and gradually (very gradually) increasing the mileage, making sure that everyone is still having fun. Make sure everyone is comfortable with the right clothes and gear. If something doesn't work, make sure that they know you care, and that you are determined to help them solve the problem. Go car camping regularly (try to combine it with some day hikes) and gradually scale back your gear and food preparation (again very gradually) to the point where you are car camping with backpacking gear. Get everyone very familiar with the equipment, the food, and the clothing in a non-threatening environment so that when you actually get out for a backpacking trip it looks just like a car camping trip only without the car. Again, if something doesn't work, make sure you acknowledge the problem and show them that you care and are genuinely interested in helping them solve it so that they can feel comfortable.
Our family hasn't been backpacking together yet, but we are now at the point where everyone really wants to do it. We just have to make a few more gear purchases (as finances permit) and we will be ready to go. In terms of thru-hiking, I told my wife that when our family can hike the 100 Miles Of Maine (the last 100 miles of the AT - we live in Maine) I think that we would be ready to attempt a thru-hike. She liked hearing that because she knows that we now have a proving ground to determine whether or not it would be possible for our family.
In between the hiking, there are many other things you can do to encourage life in the outdoors. Things like walking or cycling to work (all year round), gardening, etc. All of these things work towards your family appreciating being outside.
In terms of jobs, security, etc. I am not sure what the answer is to that. If your job offers you the flexibility, then great. If not, then you have decisions to make. What is most important? As others have said, if you really have goals, and are willing to be creative, there are many ways you can do things. It all comes down to what trade-offs you are willing to live with. If your entire family now wants to spend more time living a life of adventure (because of all of the good experiences you have been able to provide for them), they will also be more receptive to making un-conventional changes to support those family goals. I guess what I am trying to say is that if you get the entire family on board the whole process will be a lot easier than if it is just you.