From the Car park at the Quay take the exit on the hill side of the car park and just follow the track alongside the Tamar River.
Bin for dog waste provided. 
Walk can be a bit steep in places after the viewing point.
Pass the old Edgcumbe Chapel.
Round the valley to the viewing point overlooking the Calstock Viaduct.(See pictures)
Continue on up the hill and down to lower kelly.
From here you can turn right to Calstock and the pubs.
Or turn back and retrace your steps. 
Or turn left (West)  up Danescombe valley. There are several trails from here on the left side up the hill and back to Cotehele Quay, with rustic benches provided to catch your breath.
Or continue all the way alongside the stream to Danescombe Farm, at the road, turn left and in 20 yards left again, through the gate onto the grassed path on the other side of the valley and back to Cotehele Quay.
Edgcumbe Tea Rooms where dogs are welcome.
In the summer there is usually a shed selling great, proper, Ice creams. 
Toilets. Picnic area. Visitors centre.