Overnight stop at the port in Caen

Gandam

We are travelling from Portsmouth to Caen very early January next  year, arriving in Caen at 9.30pm. I have searched this site for overnight stop ideas, have followed all the links and e mailed a few sites near to the port. The problem is they are all closed
at this time of year. It looks like we are going to have to stay in the parking area of the port itself. My questions are: Does anyone have first hand experience of doing this, where do we go, are there any facilities available or should we take a small container
of water. etc . Also we have a dog so does this present a problem? I should say we are a car & caravan not a motorhome. Any help or past experiences greatly received as this is our first trip abroad with van & dog.