I feel that in your 40s with 4 children, you are past the economically viable years. Yes, you can do it. Take out a student loan for a PGCE... But what's the point? By the time you qualify you will be the least experienced teacher on the staff of any school and likely one of the oldest, older than the head or deputy if an ordinary primary school. At best you've got a 5 or 6 year career on a salary in the 26k to 32k range over that time..
I've taught in 5 schools from 2001 to 2017 with a gap in the middle... None have any staff now aged 50+. Even the army of dinner ladies and TA's have morphed from very capable ladies in their 50s and 60s to young mums in their early to mid 20s.. if indeed there are any employed in those roles.
I don't want to be cruel, though sound it, but for a 'career' in teaching you've missed the boat... It's a sub aged 35 career now, someone without parental responsibilities, elderly parents responsibilities, likely without a mortgage and still renting... Yes, you can try it for a few years, but the money isn't worth the effort and bother... The PGCE is a breaker.
And regarding jobs overseas, they are mostly private schools wanting experience of working in UK private schools for a good 2 or 3 years... Competition for those tax free jobs is fierce, often against 30 somethings with 8 or 9 years in the classroom who need to save serious money for a deposit. Before you can get an overseas job you'll need experience of a UK private school or good academy or grammar... To get that job you'll need to know about common entrance, scholarship exams, Duke of Edinburgh awards, etc etc...
My advice, don't get ahead of yourself. There's a long journey to get that job at the end in Qatar or UAE, and your odds are much lower when you are up against 20 or early 30 somethings who can offer after school activities a-plenty, are unmarried, have no visa issues with a spouse or educational requirements for their children.
Harsh, but how it is.