: You could also not bother pre-cutting the curve and just do all the shaping
: with a sander or plane. But this is a lot more work.

This is one area were you have an oportunity to learn how to use some "clasic "tools. A Draw Knife and spoke shave make easy work of paddle blades. I can carve a canoe paddle with these tools plus a block plane in about a day. The draw knife is an extremly versitile tool that people have forgotten about. You can hogg out some serious wood when neccesary and then fine shave with it as well. I even use it for inital turning down from a square to octogon of the handle. You can get one from lee valley tools or an antique shop. You sound as if you enjoy the woodworking aspect of this project so i think you'l love learning how to use these tools. Once you get use to them- you'll find more and more uses.
Cheers
Rick