Manitou Beach is a secluded community of very nice, upscale lake-front homes and behind that some newer (1980s) housing tracts. It is a very quiet place to live (we have some friends who have lived there for years).
There is virtually no crime in the area. The whole region is in the top 10% of safe places to visit in Western New York State. There are no repetetive major crimes (violent nor non-violent). It is just a nice place.
You should have no problems when visiting Manitou beach if you just do the same things you would do at home to feel safe. Enjoy your visit.