First of all, that may be the cutest little thing I've seen!
Now, back to the wood. Mahogany has been used for eons on boats, so don't be afraid to "use what you got". The key to mahogany, imho, is the grain cut. I used a 1/4sawn piece to fashion a tiller, because I believe that to be strong enough to withstand the pressures of the helm. Of course, finishing the wood properly will aid in it's longevity. That and not being lazy about maintaining it. I used several heavy layers of Spar Urethane and it seems to be holding up fine.