We are 2 married couples who are looking to visit Athens and the Greek Islands in late September or early October. It is not that important that we swim, however, we often enjoy snorkling during our travels in warm climates. Our main focus for this trip is to visit the beautiful sites one reads about and visit the famous Greek ancient historical sites. We enjoy self-exploring/discovery, hiking, and not becoming tied to a formal touring group. Is September or October a wise time of year to travel to this region?