The alley between Waewaetorea & Okahu Islands - great diving

Roberton Island - also great diving, and a nice walk up to the lookout 

Hone's Garden - amazing pizza & local beers 

As for fishing, I've been up there a few times with the boat, but don't have any specialist knowledge. I've always done OK though. Don't think you'll struggle to catch fish. The islands do provide shelter, but it can get surprisingly rough, so keep an eye on the weather.

Russell is the place for you. 

Accommodation should start becoming available in the second half of January. AKLD Anniversary Weekend could be busy though.

Plenty of old heritage type stuff to check out, shops for, err, shopping... a few cafes etc for, err, cafe? Youve got beaches on the islands, or on the mainland in Russell and out at Oke Bay. Surf at Taupiri/Elliot if you get a big easterly blow.

Launching for your boat is at the ramp in Russell or at Tapeka. If its screaming S/westerlies those ramps will be exposed badly so, 20mins east at Te Uenga is really good if you have awd/4wd - and will launch you right into the islands and protected waters.

Drink, but dont eat at the Duke. Youre better off eating at the Swordfish Club, Hones or RSA - actually pretty much anywhere is better than the Duke.  Visit Carl over the hill at Long Beach in his caravan for your morning coffee. He's there daily before sun up. Go to Paroa Bay Winery for dinner if you want something really flash for the big night.

Fishing for snapper will be fairly tough in January - perhaps visit the Screaming Reels shop in town for the latest news and to get some bait. But ive found evening fishing in 50-70m between Red Head and the Ninepin in the evenings and even after dark with fresh bait seems to be fairly reliable for snapper. Or focus on Kingies at Bird Rk and Piercy with Rapalas and livebaits during the day - unlikely to catch a monster but plagues of ~12kg fish over summer.

Boating - but not focused on fishing - is usually protected no matter what the wind. As mentioned above, Roberton Is interesting, as is Moturua Is - both good in a northerly wind. Waewaetoria good in almost any wind - great beaching and swimming etc. If it turns east - move to inside Urupukapuka Is - that also has food and drink at Ohehei Bay with some good walks with stuff to check out.

If its calm and youre feeling confident, blast out to Cape Brett and run the hole through the rock.

Fuel is at the GAS at the Old Russell Rd turn off. They now have 24hr pay at pump so you can go early or late.