If you are staying in Cebu City, there are many different tours and activities available. First of all, if you love the sea, then you must go Island Hopping. It involves renting a motorized pump boat that would take you to the different islands near Mactan. A couple of these islands offer marine sanctuaries for snorkelling or diving and also picnic areas for lunch.
For history buffs, city tours are available taking you to different historical and cultural spots in the city such as Magellan's Cross, Fort San Pedro, Santo Nino church, and many others. You can also squeeze in a visit to TOPS, which is a nice lookout located in Busay Hills, where you can see a panoramic view of Cebu City and Mactan Island.
For those that love small towns and nature, a day trip to Kawasan Falls in Badian town is recommended. Badian town is three hours drive along the scenic south coastal road. A short fifteen to twenty minute walk along the scenic & peaceful Matutinao River takes you to the falls where you can swim or go water rafting.
Another option would be a whole day tour to Bohol. It involves a two hour fast craft ride to Bohol where you can see the endangered tarsier, the Chocolate hills, historical churches, and more. Lunch will be served on a floating riverboat while cruising the Loboc river.
With these different Cebu tours to choose from, you are sure to be able to customize and maximize your trip to Cebu!