The Milltown Gorge on the lower Arahura has been used for years by teaching groups and offers a nice trip for novice paddlers on the coast rather than driving shuttles or sitting at helicopter pick ups. The gorge itself has a half dozen or so Class II+/III rapids with some fun little play spots and good practice eddies. Good play boating when really high.
The best way to shuttle is to ride a mountain bike along the forestry road which parallels the river (but has a locked gate you have to climb over) this takes about as long as driving and is better for your health! The car shuttle is a little complex and you’ll probably want to go to the take out first.
From Hokitika: head north on SH6, turn right on Arahura River Rd road (just before before the Arahura road/rail bridge). Drive up that road about 8km and onto Humphries Gully Rd. When the road turns to gravel continue on for 1km to a red shearing shed with a gate on the left. Walk 200m along the 4WD to the river and identify the take out.
To get to the put in: Head back a short distance and turn left on Blue Spur Road. Follow this until you pass the Stations restaurant then shortly after turn left on Hauhau Road. Follow this until you meet Lake Kaniere Rd then follow directions as for the Arahura put-in. Put in anywhere along the road on way to Arahura put in.