There are no assumptions in cyberspace. Not about the age of engagement. The 55+ user demographic is rising fast, as a population with the discretionary income, the time, and the motivation to learn and stay in contact is raising the age bar online.
Where is your audience, and what is there level of engagement? Here’s a quick overview in an article on differences between Facebook users and other social network users, highlighting their personal, social and online lives.
Are you “fishing where the fish are”?