we usually do:
yum cha at jumbo
then to stanley market
after that head to the peak (i have a car, makes it MUCH easier)
if you are doing public transport, then take the tram DOWN to central
ferry across to TST, walk along harbour, then down nathan road (should be dark by that point)
temple street night market
do you really have no ideas about where to take them?
you can also do:
dinner in sai kung or on lamma
tram to big buddha
forget a junk trip, too expensive, take a bunch of ferries instead:
ie) star ferry central-tst
star ferry tst-wanchai
ferry wanchai-kowloon city?
ferry north point-kwun tong etc
get on the tram and see where it goes, a FANTASTIC yet cheap way to see the north of hk island
a trip to shek o beach
monkey hill in kowloon
computer shopping in golden centre, sham shui po
mongkok (personally HATE IT, but always take visitors)
a hike in one of the MANY country parks