I had 3 days kayaking in Abel Tasman and 4 in the Marleborough Sounds in Feb and had an excellent time. I definitely recommend freedom hire if you've any experience at all, it gives you more options.
I was going to with the outfit at the Northern End, but at the time the business was changing hands and they didn't do rentals for longer for two days. We hired through MSK at Marahau.
Depends on your experience and conditions (the prevailing wind's from the north) but you should be able to get to Torrent Bay in a day, and two days comfortably to Bark Bay. From memory most do one way rentals.