Ah, GSIS... forgot all about that one. That makes a lot more sense!

School starts around 8:30am, so generally kids are there for 8am... so the school buses leaving around 6:30am~7am is actually about right... takes about half an hour to get up to The Peak from Central.
Costs of Hong Kong... yeah it gets expensive if you live here with an expat mindset. The more "local" you are willing to go, the cheaper it is... since the average office worker earns only 750~1250CHF/month (6k~10k HKD/month) and they have to live/eat/travel in the same city!
Thankfully electricity is cheap... for an average flat (70sq.m), even in the high of summer with air-con all day and night in all rooms, the monthly bill should still be under 250CHF/month (2000HKD/month). This is one advantage of living in a village house is that they are generally in the "country side"... so during summer, I can have the windows open and the natural breeze does quite a good job anyway! So a "green living" electricity bill could be well under 38~75CHF/month (300~600HKD/month) even for a family. Water is very cheap, around 20CHF/month (160HKD/month... no typo!). Gas would be around 45CHF/month (360HKD/month), but HK village house don't have mains gas... so they are either electric hobs or use LPG canisters.
Internet/TV/Telephone bundle will be about 40CHF/month (300HKD/month... plus more for whatever subscription only channels).
Taxis are still (compared to anywhere else) cheap... it's now 2.50CHF (20HKD) flag fall and ~0.2CHF(!) (~1.50HKD) for every kilometer. So even a journey from Central to The Peak would only be about 6CHF (50HKD... assumes no traffic jam!). A long 35km journey from Airport to downtown through a toll bridge and toll tunnel is still under 45CHF (350HKD).
Typical bus ride is about 0.80CHF (7HKD)... longer journeys (like New Territories to Hong Kong) are under 2.5CHF (~20HKD). Metro/Commuter rail is generally a little cheaper for comparable distance, compared to buses.
Food. A reasonable Western restaurant/gastropub would be about 12CHF (100HKD) for a set lunch and 25~38CHF (200~300HKD) for dinner, per person. Beyond 40CHF (350HKD) per person... that's getting into 5-star hotel all you can eat type buffets... HK spoils you like that!
Eating local. Dim-sum type lunch can be had for 2.50~5CHF (20HKD~40HKD) per person. Full on Chinese evening meal, 10~20CHF (80~160HKD) per person (I think the last time I was in Lamma, the seafood dinner I had with 3 other friends came to 75CHF (600HKD) for all of us).
As you're a family, you might consider a domestic helper to do house cleaning etc. A part-time local Chinese cleaner is about 7.5CHF/hour (60HKD/hour). Alternatively (and a lot of HK Chinese middle class and general expats) is to have a full time live-in maid (usually Phillipino, otherwise Indonesian). Chinese employer wages are about 475CHF/month (3800HKD/month)... expats are a bit nicer at 500~750CHF/month (4000~6000HKD/month). They'll obviously live with you, but it isn't unknown (and quite common) for them to take the child to/from school, do the grocery shopping and even the cooking.
Lastly, a two year stay works out quite nicely for home rental as the contracts are also for two years. 1 year is contractually required, so if you cancel the contract, you'll forefit the remaining of that 1st years rent. Alternatively, if the landlord breaks the contract, they own you (this happened to me one and I got some money...

). The 2nd year of the contract, either party can terminate the lease without penalty as long as there is 1 month's notice. Also budget 4 month's of rent "up-front". At the extreme, it is 1 month in advance. 2 months as deposit (which you get back t the end of the lease) and 1 month to the real estate agent for "finder's fee". There are a few other permutations (which all work out cheaper)... but forewarned is forearmed!
I'll be having some visitors from Brussels in early April, but if you are here whilst I'm free (say later on in that month)... give me prod. Am happy to help out.