[mothered]

My only concern is that both are being delivered by AusPost, likely on the same day. Will contacting both companies for DNA be unadvisable?

It's no different to purely SEing a given company - never do It In close timing.

The same applies to the carrier, especially In this case being on the same day.

Do I have any other options? (Nike 6 Items of clothing ~$400, MyProtein 3 bags of protein and 1 shaker ~$200).

Given there's 10 Items that you'd like to SE In one hit, the DNA Is the only option.