Handpicked Festival - Query on Special Offer Code

I have some friends who are interested in going to the Handpicked Festival this Saturday at Langhorne Creek in South Australia. On the website, there is a spot to enter a Special Offer Code. If anyone knows what this code is, then this would help out greatly. They want to take their kids to the festival, but because they are over 13 and there are no concession tickets, it would mean that they would have to pay over $360 as opposed to $180 for the 2 parents. Any help would be greatly appreciated.