travel plan to Sydney, Australia

You will have 5 days in Sydney so that you can have enough time to travel around Sydney and its surroundings. You need to spend around 3 days in the city centre of Sydney. For example, Harbour Bridge, Opera House, Rocks District, China Town, Darling Harbour, Manly and Bondi Beach, also the Taronga Zoo and Blue Mountain, all of them are worth to visit.
For other 4 days, I recommend you to join the local tour. If you want to visit vinyards, then you should go to Hunter Valley. There is some one day tour in the travel agency in China Town. It's not too expensive and you can try it.
As you will go to Sydney in late September, it's the season to watch the whales and dolphins in Port Stephens (2 hours coach from Sydney), of cos there is local tour also in China Town. I remember some travel agency will arrange 2 - 3 days tour to both Hunter Valley and Port Stephens. You can get some information after arriving Sydney.
For Melborune, as the previous answer, usually you need to join 2 local tours. The first one is going to Philip Island to watch the penguins at night. The second one is going to Great Ocean Road and gold mines.