I just spent three weeks in the Caymans and stayed at Sunset House. the diving out front is marginal at best on the shallow dives. deep wall dives where great.
I also dove with Dive Tech and they where fantastic to dive with.
the diving is at the Turttle Farm and is incredible just off shore.
good snorkling too I pressume.
One adavantage of staying at Sunset House is that it is within walking distance to town. however a car to rent is only $20.00 per day. cheaper than one cab ride top town and back.
The wall diving on the North [i think] side is great. Tarpon Alley etc.
what ever you do don't miss Sting ray city I save it for a fly day as it is only a 10 foot dive, but incredible.
There is another place about two doors down from Sunset House that is owned by a couple Dan and Tanya [Of freediving fame] I can't remember the name but others might fillin that blank
they are really putting out a good experience, and they are great people. I am sure you will find this place much more economicaly priced.
for the non diver, well they have a movie theater that changes the flick once a month, and there is shopping [hope the color of your card is platnium]....i might suggest staying on 7 m ile beach where she can lay out and meet some nice people who also don't dive.
There is nothing to do there but dive, and the diving is amazing