I have used closet pole paddles like these- with curved blades. I put pvc rings around them as drip stops. It's very quick and easy to make them by cutting the curves in the dowels with a jigsaw or bandsaw. That is stiff enough to become a self-form for curving the 1/4" plywood blades. It's quick and easy and will get them going if the boat is the main focus of the class. GP paddles or nice euro paddles are probably a class unto themselves.