I'll be pulling the shaft out to replace the sprocket so I will probably do what basic repairs I can do to improve the keyway issue. Then fit the wheels and try drilling a pin in. Will probably have to remove the tyre and drill through the rim to get a clean shot at the hub. Wonder what a new shaft costs?.

What do other brands of ride ons use to attach drive wheels to the shaft?.

Pity they weren't steel rims....a strategically placed bead of weld would have sufficed.