You don't DO anything on Corfu. You go to cafes and restaurants that overlook the sea, and drink retsina. And eat appetizery stuff, and have fish and salad for your main course.
You can also go swimming or sailing. There will be cute donkeys, but there isn't really anything to do with them.
I agree with Janice, there’s lots of swimming and beaches. There’s also Angel’s Castle, a Byzantine castle on a high hill with stunning views. There’s a lot to do in Mykonos, but that’s another 6-7 hours by ferry.