We have snakes around and about. They help keep the chipmunks and rabbits under control. I see one every now and then, usually a black snake.
The chickens ate one last year. This year they watched one slither through the yard, through the run, and into the neighbor's yard. All my chickens are mature. I doubt a snake would bother to mess with anything it could not eat.
You have to do what you have to do. If you feel unsafe with the rattler there, kill it or have someone else do it. Most people who are bitten by snakes knew the snake was there. In other words, don't mess around with the snake. If it feels threatened, it will bite. Get it on the first try.
Chris