You guys may have to rethink the times you plan to get there for the 'pit' area. I can not say for certain this is how it will be in Melbourne, but here in Adelaide yesterday, the pit was the area wristbanded and they only allowed the FIRST 2,000 people in there. No wristband, no pit entry. Daughter no. 2 went and they were there by a bit after 10.30am. All the pit area was done by then.
She said that there was probably 2,000 ppl in it but there was plenty of room. A friend of hers made it to the front barricade [got there at 8am to line up] and because they were in alarge group of about 20, they had no probs going for toilet breaks and the like...apparently the whole thing was handled brilliantly well by all accounts.

As I said, I can not say that will be the exact same for Melb. but I'd think it would be close.

Cheers,
S.