Berlin Tegel Airport is the city's closest international airport. From here, the city centre is just 20 minutes away by bus. If you are flying into Berlin Schönefeld Airport, then the journey will take around 25 minutes by train.
The city also has good rail links with the rest of Germany and neighbouring Europe.
Once in the city, bus numbers 165 and 265 will take you to outside Treptower Park. It is also possible to get the S-Bahn to Treptower Park.
Yes, absolutely. As long as those under 16 are accompanied by a parent or guardian at all times, there is even a whole Kidzpalooza section dedicated to young festivals fans aged 0 to 14.