Really? This just proves the point of the grandparent comment. I can think of at least three types of activities off the top of my head: sports (granted, not all of them, but definitely true for my sport - squash), music (playing an instrument in a group setting), and volunteering. I also know people who are in a bridge club with people twice their age.
There are still social activities connecting people of different age groups although I agree with the above comment that structurally the society we have has been eroding non-labour market interactions.