About 65 kms north-east of Melbourne is the Kinglake National Park. Well worth a drive if you want to get out of the hustle and bustle of the CBD and get into nature.
We headed to Masons Falls where there are about 13 kms of trails to walk, however we just wandered along the path (about 1.4 kms round trip) from the picnic area to the viewing platform at the waterfall. You might get lucky and spot a lyrebird or two, unfortunately we didn't despite looking hard, although we did hear them. A wallaby hopped across the path in front of us though which thrilled the kids (okay, and me).
You can get more information about Masons Falls and Kinglake National Park on the Parks Victoria website.