The Moominworld is located in Naantali, just 16 kilometers from Turku, easily reached by your own car, bus or (in the sumemr time) steam boat Ukko-Pekka. The Moominworld does NOT have any rides or amusement machines, but the smaller kids who love The Moomins will love this place.
Nordic Light Hotel is a great place for meetings, especially if they are long and you need to maintain a high level of energy and creativity throughout the day. The hotel is located just outside the railway station so you'll be there in half an hour if coming from the airport by Arlanda Express. The facilities, refreshments/snacks and the view over the city (10th floor) are magnificient.
Small kids will love Ti-Ti Nallen Elämystentalo, next to Ikaalinen Spa. Suitable for even small kids (my daughter was 2.5 when we visited there). Not open every day so remember to check the opening times from the website before you go.