We went to Phillip Island over Queen's Birthday - DD loved it. There's a nature park there where you can feed the animals, there are a stack of kangaroos and wallabies that you just wander around with. DD is still asking if she can go and play with the "Kanaroos" At San Remo there's pelican feeding daily and a great fish and chip shop. We were busy the entire trip (4 nights) and we didn't even go to the Penguin Parade.

I'm pretty sure the Big4 Bellarine one won the best caravan park in the state at some point too. Been to the sound and light show at Sovereign Hill, but without DD, and it's awesome. But noticed that Sovereign Hill is getting pricey too ($42 for an adult ticket!). As far as the city goes, you could do a river cruise, or jump on the free city circle tram, even the zoo.

Have fun!