I will also be going to Tasmania (Hobart) in July for a few days - but my traveling partner and I are not as resilient as your family; we're coming from the Los Angeles area to Australia so we're not accustomed to the cold weather in July.

The only "wild" penquins that I know of in Australia is the penguim sanctuary on Phillip Island outside of Melbourne. It's called the Penguim Parade and the tour is offered by many tour operators. The wild (world smallest penguins) penguins have several nesting areas on Phillip Island and you can watch hundreds of them run back to their nests every evening after a long day of hunting out in the open sea. There are viewing stands along the beach and you'll be able to see them swim to the shore and run back to their nests at sunset. I would highly recommend going if you have a stop at Melbourne - I went there three years ago and thoroughly enjoyed watching and learning about these animals.

Have fun on your trip!