There's no problem parking the car at the docks, and no need to notify us or Dollar.

The only thing I would say (not to worry you, and very unlikely to happen), but in the unlikely event the car is broken in to, then the cost of windscreen repair is not covered in the insurance, so you might bear the cost for this (the car itself is covered if stolen). See http://www.uscarhire.co.uk/faq-inclusions.aspx#126 for details of this.