You're going to struggle with the 4 year old getting into a "top" school. I think for ESF which is the formerly gov't subsidized English language school system, applications for Year 1 entrance next year have already closed. But please check this at their website. Kellet which is the main British international school is impossible, people apply at birth. I went on a tour there and a couple with a 4 year old who were moving to HK were told without a $500K debenture impossible to get in.
I would suggest for schools:
- Nord Anglia International School (Kowloon) - UK/IB
- Hong Kong Academy (Sai Kung) - IB
- International College Hong Kong (Hong Lok Yuen) - IB
As noted above, I live in the Gold Coast and for several months last year (before an unrelated injury) I cycled to work every day - 18km down a road (no cycle path). I have a sports centre opposite my office and used to shower there before going in. I'm a very slow cyclist and despite this being an almost flat 18km, it used to take me over an hour.
Now for the "no". On HK island its very hilly, so the only people who cycle are mad enthusiasts who get up at 4am to avoid the traffic and still sometimes get hurt.
In the NT, where there are cycle paths you will often find people walking on them or at weekends in particular, very slow cyclists with NO CLUE what they are doing. That goes for the pedestrians as well. Complete lack of spacial awareness. Its problematic on cycle paths.
In my commute, which was on the road, this translates into taking ones life in your own hand, as road users here in HK are also completely specially unaware, have zero understanding of bikes and are generally asshats. I generally arrived at the office shaking. I persevered because I wanted the exercise, but will struggle to convince myself to have another go.
BUT -if you are a fast cyclist with excellent road sense and used to bad drivers, you should be fine.
I wouldn't cycle on Hong Kong roads anywhere, especially Kowloon or HK island. I find it scary enough when I'm in a vehicle.
Since this move will impact your family, I would suggest you bring your family to HK to explore for a couple of weeks. I have children of a similar age to you and I wouldn't uproot them to a place in HK unless there are compelling reasons (brexit).
And maybe one little thing: Don't be scared by the idea of living in high-rises. It's actually quite nice and safe.