If your toes are pointing to the outside there's a good chance your heel will touch the crank. Some pedals offer various settings to adjust the 'q-factor', that's the technical term for the distance between the pedal and the crank. The most usual method is via the cleats, the same cleat attached to the right shoe offers a wider q-factor than if attached to the left shoe.
Note that the cleat threads are not positioned the same way on a different shoe brand. My feet used to touch the crank when I was using Pearl Izumi Vagabond shoes, since switching to Sidi Genius 5 they don't touch anymore.
I would advise working on the shoe and cleats before buying a shaft extender. An extender may cause an armful effect on your hips (too much q-factor) and weaken the pedal to crank link (loss of stiffness).