I would certainly visit the Jumbo Centre. Nice bars and restaurants to have a drink or something to eat.
Book a boat trip and see dolphins and whales!
Visit palmitos park.
Take the taxi to Maspalomas (the nereby "city") where you can eat or have a drink. This is a luxurious village. There also is a shopping centre with shops as Prada etc.
For Dutch people: visit the Heineken Cafe (with also a restaurant with Dutch meals) at Gran Chaparal or the Shooters café in Kasbah.