Minimum tools would be a coarse rasp (with a rounded face on one side) , sand paper, and borrow a jig saw to cut the basic shape. A spokeshave is perfect for the job and a very safe tool to use. A draw knife is over-kill for the project and dangerous in the hands of the inexperienced. (plus you easily ruin a good start on a paddle)

5/4 pine x 3" x 6' for a child is perfect. Or mill a 2 x 4 of spruce etc. You might as well use a decent piece of knot free wood because the labor involved makes it worth it. My first GP was from a piece of spruce I found in a dumpster with a few tiny knots.