Montpellier city centre is just a 15 minute bus ride away from Montpellier–Méditerranée Airport. Bus number 120 will take you into the city centre.
The city is also easily accessible by rail from the rest of France, although some journeys will require a change at a major city.
From the city centre, you can reach the Parc des Expositions via Tram line 3, or a ten minute taxi ride.
Yes, those under 16 may not attend, and those under 18 must be accompanied by an adult.