1. Akureyri

Akureyri is the biggest town of the northern Iceland and the biggest city after Reykjavik and its surroundings.
Just outside Akureyri (heading east), there is a very nice spot called 'Kjarnaskógur Woods'. It is a big area where it is nice to walk around and play.
The swimming-pool in Akureyri is one of the most famous one in Iceland. It is very well equiped, with many geothermal hot pots, a Turkish bath, waterslides, a children's pool as well as an indoor and outdoor pool.
Close to the swimming pool there is a family garden with popular playground equipment.
It is very nice walking around and seizing the atmosphere. You can sit down at a café in the 'pedestrian-street' downtown or count the stairs up to the church. It is also possible to have a guided tour around the town.
Other activities might include bowling, horseback-riding or sea-angling.
Akureyri has a good ski-area close to the town. Just drive up to the mountain above. It can also be fun going there during the summer, just to walk around. You get a bird eye view over Akureyri and surroundings.
For more information, please check this web-page.
From Akureyri there are scheduled tours to Húsavík, Mývatn, Ásbyrgi, Dettifoss and other places. As the road to Dettifoss is not very good I would recommend an organized trip if you are in a small car. Check for example this web-page.