It is a very difficult question, as I'm sure you are aware.
The "usual" migration is the occasional application programmer getting into the system's side, as the employer wants to keep them but they want more technical challenges. I've never found anyone going the other way.
You have excellent reasons for wanting this particular type of job, which is to still be able to be active in your son's day-to-day life. As with your decision to stay out for six years, I commend that decision and think that your son will really benefit from the time you have spent and want to spend with him, while still wanting a job/career.
In Europe and the US, many employers are "family friendly", and there exist schemes like part-time work, job-sharing, tele-working, etc.
I think you have to think of ways to be creative in presenting your requests for work. Highlight the time-out already taken and the hours that you want to work to show that you are a responsible, thinking person. You're stuck with those things, so make a virtue of them.
Another suggestion depends on you. Back in the 70's, I think it was, some women in situations similar to yours set up a company called F-International. How about hunting out others locally in your situation and seeing if you can pool ideas, find employers who are more family friendly, or whatever else you can think of between you. If you set up something, you can try to get newspaper articles published about the particular problems of accomodating your type of work to a family, when the "noraml" hours are those of a foreign country. Aim to get on TV. Maybe then employers start contacting your group.
Also do what you can to "hone" your skills. Look in on the "sister" website to this one,
http://ibmmainframes.com for instance.
Should you train for something else? That is something for you to plan for. There are costs there, as well. Maybe more work, though, if you choose the right thing.
Take some time to think things through. Plan. Design. Use tools you have, or can make available. Use the thinking skills from your job to get some short-term, medium-term and long-term strategies together. Think about what might happen that requires the strategies to change. Be creative, think creatively.
I hope this helps rather than hinders, and I wish you the best that you can achieve for your future.