The offers in Vassiliki, Lefkada and Nidri are so immens that you don't have a chance to try everything in a few weeks.
You've lots of possibilities for sailing (island-jumping), windsurfing, diving, waterskiing, swimming, rock-jumping and water-paragliding - but other sports like mountain-biking, trecking, horse-riding or beach-volleyball give you multiple choices to create your personal-styled holiday..
If you like it more quiet, you can relax in uncountable, less visited bays, visit monastries in the inner of the island, or have shopping-trips to Lefkada or to neighbour-islands by ferry-ride. Or just read a book in the shadow of an olive-tree...
And after all, you find a nice and varied nihgtlife in Vassiliki: Some nightclubs and bars with different styles of music, billard-rooms, beach-parties and of course privat invitations if you don't wanna miss the chances for Greek-English-German communication.
And every year in August there's a large Folk- & Culture-Festival in Lefkada-City.
Have you ever tried Windsurfing? It's easy to learn in a few days it in one of the surf-shools of Vassiliki, and later you will remeber: "I had an awesome time in Vassiliki!"