I visit Greece for the last 15 years. Volos, Pelion and Sporades are my favourite destination. The distance from Volos Airport to Volos town is about 40Km. Google maps are really mistaken here. I usually pay 50euros to get to town by taxi. Bus transportation isn't something I liked in Greece. As a taxi service I recommend www.taxiinvolos.gr , I used them last year and this one, excellent english, new mercedes car, really polite and very helpful, email them , I am sure you'll get everything you need.
By the way you are going to have a great time in Pelion
KTEL has buses from the Volos bus terminal to the airport. At the airport go out of the building and 50 meters to the right, there was no sign, but people will be wating there. Bus itineraries are planned to arrive at the airport according to scheduled flights.
Most people use volos as a means to getting to the pelion, as planes to volos from the uk arnet very frequent most people either fly to skiathos or to thessaloniki. We recently went backpacking in the pelion and flew into thessaloniki airport and took a bus to volos. Once arriving in volos bus connections to the pelion seemed to be timed to meet the busses fron thessaloniki and athens. The busses to kala nero platanias and the pagasetic gulf side of the pelion were pretty frequent, we traveled all round the pelion by bus but you are limited to which villages they pick up and drop off in and on the med side. What we did we found a base and then hired a moped which had no problem with the steep climbs and was a great way to travel as the roads in that area are very quiet.
Here, one can rent Bicycles, Cars, Motorbikes, Scooters, and in certain places (weather permitting), Watersports equipment is also available for rent. Public transportation is also accessible on a regular basis. All over Greece, it is also possible to rent boats, yachts (with captains), and docking space for private boats, in the harbours.
Since 1998 Volos airport is open to commercial flights. It is a militairy airport, so don't take pictures!