I appreciate a lot your inputs. I understand that our situation could be seen as a bit awkward. Maybe I should explain a bit more.
For the past 6 years we have been living abroad (I mean not in France) and our last expatriation is coming to an end. Normally the family should go back to France but my job offers us another option. I will move soon to a 4 weeks on / 4 weeks off rotation, meaning I will work by period of 4 weeks following by 4 weeks of holidays following by 4 weeks of work, etc. As my wife wishes to carry on with the expatriate life style as much as possible, it is possible for them to leave in another country than France and I join them on my rest time. The 2 main criteria for the new residence country are a) getting an English speaking shool, b) be a nice country to live in.
Until last year our target country was Canada ans more specifically the Vancouver area. But my wife had a 1 week of vacation in Crete 1 year ago with the kids and a friend of her and she just fell in love in the country. When it turned out that there an European school in Heraklion, Crete became a real possibility. And it is now our first choice as it offers a lot of advantages (no resident visa, close to France, greta food, very nice people, brilliant for sea activities, for astronomy, etc.) provided the school is OK.
Honestly our situation is very comfortable, we give it a try if it does not work well for whatever reason, the family goes back to France where we still have our main house and the kids are registered in the local school. So leaving Crete would not be a big problem. But I am sure this will not happen.
I agree that Heraklion is not the fanciest place of the island but it is only matter of perspective. First we lived in Nigeria, then when we moved to South Korea, it appeared to be a fantastic country compared to Nigeria. And I am convinced that Crete will be even better than Korea for many reasons. Even if South Kore is a nice country and we had a great time here.
As Warwick said, Heraklion and the European school is the only viable option in Crete for us.
Like sandboy2 I am slightly concerned that the school does not bother about updating its website and I found not too good rumors about the survival of the school but this info could be outdated. That's why the first thing my wife will do upon her arrival in Heraklion is to meet the school management.