According to Zoomerang Facebook is the most used platform among all age groups. It is number one among the most-used social media among business owners in their 50s. Twitter and Likedin are among the most used social media by business owners of all ages.
So:
Under 30
Facebook 77%
30-39
Facebook 76%
40-49
Facebook 77%
50-59
Facebook 84%
60 and over
Facebook 84%