Hi All,
  IMHO, the best paddle for beginners is the (older-no longer made) 100$ seven-2 paddle with the grips. Yes, the  one everyone hates.
Here's why;
You dont have to explain feathering and rotating wrists etc. (This takes a while to automate)  
so you  can just give it to them and let them start on strokes.
In teaching rolling, they will know their blade orientation by their forward hand.
Since it has 2 grips, in teaching the off side roll, they can just  lead with their forward hand like the on side roll.
Oh, and it was cheap.

the main disadvantages were:
you need to spray paint the blades something easy to  spot and add some pipe foam to the shaft.
it is not robust enough when the person is strong and  muscling their strokes.

My second best teaching paddle is  an old ainsworth that I cut in hall, reduced the feather  and added indexing to the non-lead hand. Its indestructible. The blades are plastic stuff and can be abused and I dont care if it gets lost.

Bill