Not sure if any of the Australia/New Zealand cruises go to the Cook
Islands, but one of the Tahitian Pricess cruises does:

http://www.oladeals.com/c/1/1230/1703737_1230.htm

A liveaboard for scuba divers is definitely unsuitable for your
non-diving sister, who would be bored to tears on any of those
liveaboards.

A CRUISE, on the other hand, offers precisely the kind of
sightseeing  AND diving that may please both you and your
non-diving sister.

On each of the ports of call of the Cook Islands itinerary, there
is SCUBA diving.  These include Papeete, Moorea, Raiatea, Huahini,
Bora Bora, and Roratonga (of Cook Island).  ALL excellent dives.  

I usually book only ONE dive on each island, to allow time for other
sightseeing activities, because the 2nd dive costs the same as the
first dive (double the cost of a 1 tank dive) and there's usually
not that much new or different to see on the 2nd one.

Over a period of several years, I've made at least 4 or 5 dives in
each of the islands of Raiatea, Moorea, and Bora Bora.  Never had
a BAD dive in any of those islands.

-- Bob.

Will be diving in Easter Island (Chile) tomorrow, I hope.   :-)

Hi Reef Fish, Iam sorry for mix up I will be going to GBR and I am
checking into the  Reef endevour one of the Capt Cook boats that has 7
day cruise with stops at Dunk and Lizasrd island etc.
Thanks for info on Cook islands-they are on my list, Sara

G'day Sara,

An alternative which you may like to consider is the Coral Princess:
http://www.coralprincesscruises.com/ I know a number of folk who have
done the Townsville to Cairns leg and have had a great time. They do
provide for diving but you would need to contact them to find out
exactly how many dives are available. At least on the Townsville/Cairns
cruise they are the only commercial operator to visit some of their
their sites (once you are clear of the Cairns cattleboat zone).

regards,

John (Magnetic Island)