If you go for the speedplays get the extender plate.
If your ankle is causing you problems its a good idea to move the cleats far back, you will probably need the ekstenderplate to get the cleat far enough back.
This makes the ankle more stable, your calfs are also less used to stabelise the foot. You will lose some sprinting power but its worth the trade off.
Keywin pedals are also great for placing cleats far back. Another good thing is the way the float is in the spindle/pedalbody not the cleat moving in the pedalbody. This makes for a secure feeling of being locked in while still having some float. Entry is a breeze with a light twisting motion. Unclipping is always going to be easyer with the speedplay light actions.
Hope it works out