Any time you change careers you can expect a significant reduction in pay in the beginning. However, in the long term and with planning your income should improve. The CWI is a great credential, but you will have to obtain more certifications to improve your opportunities for employment and advancement. Advancement may be a position in management for a QC/QA department, fabrication supervisor, field management, nondestructive testing, etc. How far you advance is dependent on whether you are willing to advance your education. I always viewed my CWI credentials as a starting point, not an endpoint.
There are several of career paths for the CWI, but the most common are as a shop inspector or a third party inspector. If you don't want to travel or if you miss the wife and kids, look for a position with a fabricator. By travel, I mean you will be living out of a suitcase, traveling from one location to the next, and eating at one restaurant after another. That can get old fast, but it still pulls us back time after time after time. It gets into your blood after a while.
Like many professionals and specialists, you may have to relocate to land a position you want. The higher your aspirations, the less likely the job you want will be in your back yard. "Have suitcase, will travel" is the motto of a lot of newbie CWIs. It isn't a case of you supporting your family, it's a case of your family supporting you as you start out on your new adventure. It isn't a career change for the faint of heart. It's a difficult transition from a career as a worker that is only responsible for what you produce to a position where you are responsible the safety and well being of other people. Some people are not prepared for the responsibility that comes with the CWI credential.
Good luck - Al