Hi Plutos,
my advise if you are on a fixed contract be vary carefull to give it up. This is my personal and general advise, I would never change a firm contract for a contract job.
I am not sure if there are frensh schools in SGN but I think so.
Keep in mind that schooling seems to be very expensive and there is no education allowance offered with any of the contracts. So you will have to spent a lot of money and if you take home less than in your current job, I don't know if this is a good idea.
You should make sure that your family will like SGN and Vietnam. It's different to live in a country compared to go there on a trip.
Regarding a type upgrade, well they did it but you should better not count on it!