Everybody has their own experience of the education system here in Hong Kong and I suppose we can all only comment on our own experiences 
Some have a smooth ride and others have a stressful time of it, at the end of the day all you can do is try not to be disillusioned by the whole process.
We were also in a position that I had to arrive at the same time with the hubby 
You can use an agent in HK who can arrange school tours and interviews for you, these agents usually have tutors also that can teach your children whilst looking for a school. They do charge a fee for their services but they can take the stress out of looking for you, to an extent.
We have friends in DB who have 2 children and both go to different schools. The youngest is in DB and the oldest, who is 7, goes to school on HK island. Not ideal for the family but it's working out really well for them 
Things will work out for you in the end, I know from experience it can be very stressful at first trying to get kids a place especially when still in another country. We did find it easier when we had arrived in HK as all schools like to interview the parents and children...set some interviews up for when you arrive and take it from there.
Good luck 