There are private companies who provide hotel shuttles from the airport.
http://www.hotelink.com.hk/main_1.asp HK$140/person to HK Island.
Taxi fare is approximately HK$335 to Central, from HKG's website. So, for three, that's very competitive with shuttles and the Airport Express. There's no minivan-cabs in Hong Kong. Only large sedans (usually Toyota Crown Comfort - interior size is almost as large as a Ford Crown Vic, but trunk is probably smaller). One problem is that most cab driver have lots of junk in their trunk, so expect to fit no more than two full-sized suitcases there. However, with just you, your wife and a kid, there should be enough room to fill the rest.
A more comfortable, but pricier alternative is limo service. I have not used this, so I can't comment on the service, but according to their website, you can get a Mercedes or a minivan to Central for about HK$600.
http://www.hongkonglimo.com/html/home.html They have counters at HKG, and you can even book a car online.
Here's another one. Their website is Chinese only, but the prices and services are basically the same as the above:
http://www.hklimo.com/limo_club_price.asp Merceds S320 HK$620, E280 limo HK$720 They also have an online reservation form.
Or you may want to contact Marriott to see if they have their own airport limo service.
[This message has been edited by rkkwan (edited Feb 21, 2004).]