NZ Car Hire and Travel Insurance

My wife and I will be going to NZ for three weeks in May. My travel
plan calls for picking the car up on arrival at Auckland, and dropping
it of at Dunedin at the end of the vacation.

For car hi We're looking for a moderately priced standard late
model rental. I've seen a number of recommendations for local rentals
(Omega seems to have gotten lots of kudos), but many do not have
locations in both Auckland and Dunedin. I came across Kiwi Car Rental,
which looked good on the web site, but I've not seen any comments
about them. Anyone have anything good or bad to say about Kiwi, or
alternate suggestions?

For travel insurance: I see someone recommended World Nomads, and
after visiting their web site, I'm initially impressed, especially
since it seems to cover all the recreational activities we plan to
indulge in (also I like their sense of humor). Anyone have anything
good or bad to say about them, or have an alternate recommendation?
Some of the activities we need covered are ballooning, scuba-diving
(first time, with a licenced instructor to 12M), rafting, kayaking).
And medical evacuation in case I break my 56-year-old body trying some
of this stuff.

Thanks for any help
Larry