The choice reflects perspective. If you're conveying that the museum is serving as "host", it would be "visitors of the museum", essentially a possessive, like "the museum's visitors". From a location perspective, "of" is similar to "at"; it conveys a sense that you are writing from inside the museum and visitors are already there.
If "of" was used instead of "to", the "will find" might be different. If you were talking about a general condition throughout the museum, it would be "visitors of the museum find it easy to navigate". If you were talking about a specific exhibit that someone inside the museum still needs to locate in order to see, "visitors of the museum will find a darkened corner in front of the Planetarium..."
"Visitors to the museum" conveys more of a sense that you are writing from somewhere else, describing visitors going to the museum, in the sense of, "People who go to the museum will find..." (they aren't actually "visitors" until they get there).