Is there an alternative to washing my father's private areas?

You really do have to do this daily. This part of the body needs to stay clean, especially the backside. Anywhere that's fleshy and sweaty is prone to bacteria that can cause odors and skin irritations. Try not to get hung up on it. It's best to think about it in the same way as if you were washing a baby or a child. You basically cleanse the area quickly; you don't have to spend much time on it or scrub. Use a wipe if you prefer. Sometimes it's easiest to do this while your father is sitting on the toilet. Be sure to wash under his testicles.