Satakunta is a region on the west coast of Finland. Back in the day when boats and ships were your best and quickest choice of travel, Satakunta was about the most relaxedly international, enterprise-friendly and straight-forward part of the country. There were busy ports with international trade rights both in Pori (Björneborg, founded in 1558) and Rauma (Raumo, 1442), and River Kokemäenjoki was the highway from Tampere to the wide open world that began at the shores of the Gulf of Bothnia (via Sastamala, Kokemäki, Harjavalta, Nakkila and Ulvila, or Ulvsby, 1365).
According to some sources, not completely proven by scientific studies, but widely considered as the truth, the ancient trading places of Teljä (or Telja) and Hauho were situated - just about a millennium ago - on the banks of the river where the present town of Kokemäki now lies. Between the riverbanks and the present-day sea shore there are vast areas of super fertile land that used to be sea bed, so people from both sides of the gulf have settled themselves there, and kept in touch with their family and mates through the social media of sailing.
That was then. Satakunta now has a railway connection to the rest of the country through Tampere, which is brilliant, if you're coming from, hmm, Tampere, and okay, if you're hailing from Helsinki, Kuopio or Oulu. Just look at the map. The VR (which used to be short for Valtion Rautatiet, or the National Railway, but now I think they have decided national anything is not a good brand at the moment) trains run from Helsinki to Pori in three to four hours, depending on the connection, from Tampere to Pori in 1,5 hrs, and you can easily buy the tickets online in Finnish, Swedish or English. You can only buy tickets beforehand when the new timetables are out (about three times a year I think), and if you book the tickets 3-60 days before you go, they're less expensive. The cars are nice and comfortable, and usually there are outlets and a free internet as well as a possibility to buy drinks and snacks and light meals. Budget-wise I'd opt for buying my on-board food in advance. Oh yes, on InterCity trains there is also a car for kids, where there is a slide, a play train and children's books. My kids seem to appreciate it. I'm happy there is a place where my kids aren't the only ones making kids' noise. One child (under 16) travels free with an adult.
Matkahuolto coaches are your best bet if you're coming to Satakunta from the south or the north, or if you just prefer coaches to trains. Nowadays they have nice bargain prices (like today Helsinki-Tampere costs you only 2€), but the site says normally the 2-hour-15-minute Turku-Pori -connection will cost you 15€. Kids between the ages of 4 and 11 are half price. Again, the coaches are nice, have USB-outlets and a free internet, but usually there's no food or drinks available anymore. Buy your own.
Cheaper coach travel but perhaps not the most flexible timetables is offered by onnibus.com (Helsinki/Tampere/Turku to Pori). OnniExpress has one direct connection from Helsinki airport to Pori.
Southern Finland is somewhat surrounded by water. You can walk in or drive a car or ride on a coach if you come from the north of Sweden, Norway or the north-western bit of Russia. The road network is slowly deteriorating thanks to the interesting way the state has dealt the tax money, but they're still safe. Finland is an easy country to drive in, because most of the traffic is around Helsinki, elsewhere your main concern would be not falling asleep in the beautiful yet monotonous landscape.
But hey, there are two ways of getting here from over the Baltic Sea: boat or plane.
Most airlines fly to Helsinki, but there are flights to Tampere and Turku from select origins - even to Pori whenever there is a brave enough company to take the financial risk of few people and pricey tickets. There is a new rail connection to Helsinki Airport, so the train is probably now the best way to continue to Satakunta.
The famous cruise ships sailing the Baltic belong either to Tallink Silja, Viking Line or Eckerö Line fleets. The cruise tickets are usually cheaper than one-ways (so draw your conclusions on what's the smart way to book). There's usually a whole kids' programme with Moomins (Silja) or other walking and huggable mascots, duty free shops and a variety of restaurants, of which have never really blown my mind, but the buffet might be the safest option - you've got to eat something while you're on board! The handiest routes considering the Pori perspective run from Stockholm to Turku and Helsinki. The direct connections from harbours are run by coaches.