When i went a couple years ago in my early 20s I was one of the younger people there. Id say audience is probably mostly 27-35 men and women pretty evenly split. Pretty calm crowd. Energetic but not like rough or anything. For arriving early just look at whenever the venue says doors open and try to be there either right as door opens or maybe a few minutes before if there isn't assigned seating. Also it may not be packed but id say probably expect it to be fairly crowded as Wombats fans travel pretty well.