Firstly I am not a pilot and have no desire to be one. I just want to add a different perspective for you.
I joined the airlines as an apprentice engineer 23 years ago (In my opinion the apprenticeship is similar to the cadet pilot scheme). My first year I made about $8000. I did work two extra jobs as well as the full time hours at the airline as I was not living with parents and I had a car loan for my transport which I required to get to my full time job, and my other jobs. It was normal for me to work 19-20 hour days at this time in my life, with 6-8 hour days on Sat and Sun.
Slowly my wages came up enough in my full time airline job to the point that 5 years later I made $45,000. Another three years later (and lots of studying, courses etc) I was making $80,000. In my years since that time as an LAE I have personally spent more than $75,000, as well as more than 8 months of my own time either on annual leave, or unpaid leave on further training to advance my qualifications in order to secure better employment. I have been employed by a number of major airlines in that time and through timing and circumstance employer provided training was unavailable or too far in the future for me to consider waiting. Trust me I did not like outlaying my own hard earned money and holiday time, but I made that decision and have no regrets at all. My last job I was making the equivalent of $200,000. (All figures are AUD).
The perspective I am putting across is that you can spend money in the early years and do it a bit hard, however with the support of your wife you can succeed and get your dream job of being a professional pilot. As the saying goes....It wont happen overnight, but it will happen. If you want it to.
I know I am going to get smashed here but I would recommend the cadetship, if you are lucky enough to get selected. You wont be ostracised by the other guys unless you're a jackass, in which case whatever job you held you will still get treated like one. It is a lot easier to post anonymously on PPruNe about the treatment you will receive than it is to actually act the way towards a fellow workmate that said posters say will happen.
You will do it tough financially whilst the debt is repayed to J* (but you will get by), then you will only be early 30's and looking down the barrel of some decent wages for the rest of your life. Something would have to go awfully wrong if you did not succeed if you get selected for the scheme.
I do not wish to take anything away from the valid opinions of many posters here regarding cadet schemes, however times have changed (they changed for my profession a couple of decades before yours, except for the chosen few) but I accepted that and invested in my future which is also my family's future.
If I was in your shoes I would jump at a chance like this and accept the outlay to achieve your long term dreams and goals. I certainly would not alter a life decision such as this by placing stock on the replies from an anonymous forum. Just be prepared for the fact that you will spend a few years moving from place to place and then possibly country to country, but it will be an interesting road you and your family will travel.
On the other hand you could spend the rest of your days talking into the mike and dreaming of what might have been....
Standing by with crash helmet on...
GB