First–realize that generally it’s hot. Well maybe not today (it’s actually nice) but in general it’s pretty darn hot with humidity. This really puts a limit on how much time out you can spend with the kids before they get loggy or worse sunburned. Add to this the air pollution. In some parts of HK on certain days you just don’t want to let your kids outside (we don’t). You treat it as if it was raining the air gets so bad. Finally I should mention that we’re about to enter the raining season of Spring, so if you are planning on coming over soon you might get a few showers.
So with those caveats out of the way, Disney is a fun place. Not very crowded during the week and easy to get on all the rides with basically no lines. Can be evil on the weekends or when there is a Chinese holiday and many tourists, but we have an annual pass and go quite often during the week without any real problems.
Ocean Park, on Hong Kong Island, is another big amusement park, though with a dolphin show and some pandas. About the same price as Disney for a day pass and probably a bit of fun to do. My kids like the cable cars over the mountain, the wife did not (if you are afraid of heights it is not for you).
(note: I’d take a stroller or rent one for both places).
I’m not really sure what you want to do (i.e. relax on a beach or shop in markets or go to some malls). I’ll try to recommend a few things.
* Shek O is a very secluded beach on the south end of HK island. Clean beach and a small village with dive Thai places (plastic chairs and beer). Somewhat isolated but fun to get away from it all and just lounge on the beach. If you don’t want to go that far you can visit Repulse Bay, a bit closer and with some nice restaurants nearby.
* Stanley is a village on HKIsland with a decent if slightly touristy market. It has some restaurants along the water and a nice promenade for walking around.
* The Peak. Head up on the Peak tram (or up on a bus and down on a tram–easier). Go around sunset for the view of day and night from this vantage point overlooking the city.
* Star Ferry is the quick ferry across Victoria Harbor. Kind of fun for a kid. Largest toys r us in HK is in the Harbor Centre next to the TST Star Ferry dock.
* Symphony of Lights. Every night at 8:00 they have a 15 minute laser light show starring the major skyscrapers of the city (look on Youtube). Kind of neat to see from the Kowloon/TST waterfront looking over to HK Island.
* Tai O on Lantau island is a village on the water. You can take a small boat out at sunset and try to see dolphins (but not always successful). Many of the homes are built on stilts to stay out of the water.
* Toy street. This is a market street in Wanchai. A bit rough in that they sell basically everything, but there are about 6 toy small toy stores next to each other selling all sorts of wild toys quite a bit cheaper than Toys R Us. We get lots of Japanese robots and bullet trains and other random things here. Across from the Wanchai MTR, down the alley with the Pizza Hut and KFC.
* There are a few museums here but not quite up to the Smithsonian standards. There is a small train museum with about 8 cars and 2 engines in the New Territories, and a military museum that is an old coastal defence fort. Kind of neat.
Geographically speaking Hong Kong is relatively small, and much of the actual space is parks and mountains (i.e. unoccupied). Getting from where we live just under the Peak to Disneyland is about a 30 minute trip for example via the subway, and that’s a pretty long distance. Everything around the Island in the main part of HK is <10 minutes by cab which are generally pretty cheap. Generally most people would stay in a hotel in the Central HK area and then venture out to do things with there kids (not stay in a more remote place where there is very few hotels).
You could also do a day trip to Macau via high speed ferry. While casinos are not necessarily family friendly you can walk around the old city center which still has a colonial feel to it.
Anyway, geobaby.com and geoexpat.com are the message boards for HK expats. You can probably get some more advice there as well.