there plenty of other places to padle
While Abel Tasman is generally a low risk area and quite scenic, it can be crowded and there are many other places that are great to paddle in all dependiing on your skills.
One area I love is the Corramandel Peninsula in the North Island East of Auckland. Excellent caves, surf and hot springs! Just be aware of the swells and currents in the surf, there are no serious tidal currents to speak of.
If your not experienced and want to explore any of the Sounds, definitely recommend a guided tour, the guide should give you more than safe passage but a lot of unique information. The winds, currents and tides can make some areas no place for novice paddlers.
Babs said the peninsula east of Christchurch was great for dolphins and seals, but again choose right weather and sea conditions.
Can also recommend the Wanganui River, 3-5 days remote paddling lush NZ bush. You need basic moving water skills for this.
Good luck and enjoy Aeotearoa (New Zealands real name).