Rosebud is a top spot, I was born there. Anywhere on the foreshore in March should be fine. Then catch the ferry from sorrento. We took a similar route, Wilson's prom, Phillip island, rosebud, GOR. Didn't take the ferry because my wife had never been to Melbourne. So we went the long way to Gelong. Make sure you allow plenty of time to stop and take in the scenery on the GOR. You'll love it.