If you’re thinking of going to the theatre; cinema; event or a gig then why not ask other U3A members if they might wish to join you. This is car share with the opportunity to discuss the event afterwards.
How you make the arrangements is up to you but you may wish to follow this format:
“I’m going to see <event> on <date> so if you would like to join me then please contact me <email@example.com> or <phone number>”.
And there are many more available by searching Google…