Hi
February is still very much in summer so the evenings will still be warm. Average minimum for February is 18c. A light jacket if anything will only be necessary. See more info on our weather page. It is still the rainy season though so you can expect some rain at times which cools things down a bit.
You only get soaked from head to foot when you are at the Falls themselves as soon as you are 50 meters from the falls there is no spray. With the warm weather your shoes should dry out pretty quickly. I wouldn't buy any special waterproof shoes, normal trainers are just fine.
If anything take some slops or sandals to wear while your trainers dry out.
You can always bata these when you go for a small curio with one of the curio vendors, they love shoes!!!