Coffee Mornings work well and are relatively easy to organise.  They will work better on a weekday if your target audience is mainly retired but otherwise would be more successful on a Saturday or Sunday.  Ideally you will want to make a profit from the sale of the beverages and cakes, so best if they can be made by your volunteers.  Alternatively, you may find a tea room that is willing to do a profit-share with you.

One tip, make sure it is fresh coffee, the author will not drink instant!  (Lyons coffee bags are by far the easiest way to serve fresh coffee)