Hmm.. You don't have to be 50 to do these necessarily:
Museum - (art, photography, etc)
Dinner & Waterfront stroll
Public show (air show, surf event, etc)
Live Sports game
For the more active types:
I'd define a date-able idea as anything that allows you to share a memorable experience so that you can relate to the other person. Also, any event that gets you to chat about your lives also counts...