a bit of background about me:
37 yr female, married for 9 yrs to hk local
2 kids, 2.5 & 4.5 (both born in hk)
moved to hk when i was finished university (u of s)
i was 22 yrs old and didn't know a soul here
it is completely understandable that you will be making the move with a little trepidation. afterall, you not only have yourself to worry about, but your kids, too!
the first thing you have to realise is that it isn't the 1970s anymore. there is NO WAY your children will have the same childhood as you did. it is impossible. things change. i had this same discussion with my best friend (also from canada and contemplating a move here) a few months ago.
that said, there are a few places in hk that will afford you a similar lifestyle to what you think you will be missing.
you should look at the following:
south lantau island
southside (hong kong island)
of course, a lot of this will depend on budget...i think for someone concerned as much about this as you are, you should look at discovery bay first and foremost. i lived there for 6 years and miss it terribly. for what we need, it is now out of our price range, but it may be ok for you and your family. there are 2 residents' clubs with swimming pools, playrooms, playgrounds, tennis courts, squash courts, ping pong rooms etc. there are also two other clubs that you can join if you have the money (they marina club & the golf club). every "village" has a playground. some villages have better playgrounds than others, but there is no reason you can't go for a walk to a better one if you desire a change. there is a beach nearby that is fairly clean. i would let my kids play on the sand, don't know about in the water... prices in db are a little lower than hk island, so you may be able to get a place with a small back garden, a balcony or maybe a rooftop. there is a small shopping centre (plaza) that has all of the daily necessities and the commute to central is a lovely airconditioned ferry ride (25 minutes).
however, db doesn't suit everyone. some people love it (me) and some people hate it.
you may also want to look at sai kung. it is cheaper than db as the commute isn't as easy to central. in sai kung you could get a part of a village house, or maybe even a whole village house, depending on your budget. we now live in sai kung country park. we are about 15 minute drive from sai kung town (the closest supermarket etc). we are really out in the boonies. but we've chosen to live here because of the space that we can have for the money we pay. we pay well less than $20k/month and have 2100', garden, rooftop, 5 bedrooms, 4 bathrooms.... we would NEVER be able to afford this anywhere else in hk. our village is made up mostly of expats. there are other kids around and the village has gotten together and made a little playground at the front of the village with a trampoline and some other things for the kids to play on.
anyway, it is a very long message and i apologise. just wanted to ease your mind a little. please feel free to respond or not.
good luck with your move!