Hello Will,
While I do not have a specific recommendation for you with respect to guides/outfitters for your trip I can recommend a couple of destinations that are sure not to disappoint. Kayaking in Abel Tasman National Park, which is located at the top of New Zealand’s South Island, specifically in the Nelson/Tasman region. It is situated between Golden Bay and Tasman Bay and sure to be a winner. We rented some kayaks and followed the coast and camped at designated sites. Where we were you can’t really get lost as you just follow the coast.
At the South end of the South Island Milford Sound is spectacular and probably one the most amazing places in New Zealand.
I imigrated there in 2008 from Alberta afterbsome traveling abroad and lived their for a few years with my wife. As it has been a while I can’t offer you some specific outfitters. But with some reasearch and a call or two you will be in good shape.
Warmly,
Charles