So long as the packet for the cookies wasnt open I dont think you would get any grief for these products, but you can check the Australian Quarantine website.

They wont take the shoes off you. They will just clean them if they are covered in mud, and only if you have worn them in certain areas.

My advice is to declare the items. They are really reasonable people so long as you are honest, it is the people who dont declare things that have problems.