I live on the Mornington Peninsula as do a couple other forum members, Gadget Adam comes to mind. It is a pain driving into the city from the peninsula on a regular basis, after a couple times you will be sick of it. It will be ok to do a couple times. Plenty of places to stay in a van, I would think a foreshore park would be better, one at Rosebud is over the road from plenty of shops and the beach is pretty good. A lot of the caravan parks in the area are the ones that annuals stay at, so not really tourist parks. Further down the bay, Blairgowrie foreshore park looks nice and there is one near Sorrento that has a nice outlook. Good boat ramp at Sorrento and Rosebud. Heaps of wineries, a couple breweries as well if your into that and most of those places have restaurants. Old drive in at Dromana is good for a nights entertainment if your kids have never been to one. Plenty of eating places around. Ferry trip to Queenscliff is a good day then you have the other side of the bay, Flinders, Shoreham, Point Leo etc.