[Scully]

Our car had black tinted window and our cases are black - If you have light coloured case and leave them in the boot perhaps put a black sheet over them?
I prefer to leave them in a main Disney car park - once the cars are parked, there isn't much movement around there - you'd be unlucky to get broken into.

The car parks at the water parks are smaller and more accessible - there also seems to be more coming and going. In my view, easier for a thief to 'hang around' without being noticed.