I didn't read every post, so I am not sure if this was mentioned; however, have you given any thought that perhaps your wife would like to pursue something further in life?
I know a few families (very well) that consist of 10+ kids. In those families I have come to know, the fathers are the only one that are looking to pursue their goals and aspirations in life. However, at the same time they are leaving their wife to "take care of the home." My family has close family friends, the Johnson's, and they have 9 kids. They are in a similar situation -- the father, Tom, decided to go back to dental school after reaching the age of 40. He consulted his wife first, and they figured they were able to cash in some stocks and bonds and use up some savings in order to keep up with the finances while he attended school. He asked her specifically if she was 'o.k.' with this new career move, and she said she was happy for him.
HOWEVER, my mom and I were speaking to her one day and she expressed to us that she resented her husband, Tom. She actually started crying and expressed that she has always been the one to "take care of the home and kids" while Tom has been able to pursue his career and his dreams. She, however, has not been able to go to school or pursue a career because she has been stuck at home raising the children and taking care of the home.