Hi Jagbir,
Give 'Thomas Cook' & 'The Natural Adventure' a go . They have great holiday packages that will let you see the best of any Australian city and have flexible itineraries. If you're looking for water-related activities or cruising experiences in any of the cities, then try Australian Cruise Group. They have great budget-friendly tours.
For more: https://www.australiancruisegroup.com.au/