There are plenty of things to see and do in the Irakleidon area.
The monuments are scattered all over the region but quite remarkable. In Kardamena you can find the ruins of the ancient city of Alasarna and the remains of a few Basilica. On the outskirts of Antimachia the Castle of Antimachia and the Poria spring are well worth a visit while in Antimachia you should go to the windmill (and admire its mechanism) and the traditional house. Last but not least in Mastichari you should go for the scenic seaside walk to the Aghios Ioannis Basilica. There are also a number of impressive Churches in the area such as Aghios Ioannis Perigialitis and Aghios Nikitas in Mastichari, aghioi Anargyroi and Panagia tou Vounou in Kardamena, Aghioi Akindinoi in Antimachia just to name a few.
As most visitors staying in Kardamena and Mastichari tend to be sedentary, they usually go to the beaches in their area namely the Kardamena beaches and the Mastichari beach. For the more adventurous there are a few more secluded beaches around the Mastichari area and more specifically west of Mastichari.
There is a paved little road that links Kardamena to the Antimachia Castle. It is roughly a 45 minute walk each way and is well worth considering. Plaka, a pine forest near the airport in Antimachia, with its peacocks and cats, and cool shade is an ideal destination for those who would like to take shelter from the heat. Small kids tend to love the place, often mesmerized by the peacocks.
So overall plenty of things to see and do in the Irakleidon area, just go out there and explore.