There aren't any caravan parks really close to the Terminal. The closest that takes pets is probably the Werribee South caravan park, which is a very nice park. What day are you travelling? We live near there, during the week it could easily take an hour to get to the terminal if you leave the park later than 6am, but on weekends it would probably be 30 minutes.
We are at a caravan park in Seymour, a lot of people stay here before catching the Spirit to Tassy, because it is a straight run, down the Hume, with good signage. We left from here on Monday morning and it took us just on an hour to Coburg, gps took us straight there.
It is Highlands caravan park.
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jules "Love is good for the human being!!" (Ben, aged 10)
It's very common to see motor homes parked over night in the carpark near the Sandridge Life Saving Club on the Boulevard at Port Melbourne only a few hundred meters from the shipping terminal.