I'm not exactly sure, but I don't think the ferry opens that early? I thought it was 10 AM, but I could be wrong.
I believe the ferry does start at 10:00 but not 100% sure. While this is a few months off, I would follow the current strike situation and if it is still an ongoing situation, I would be very leery of venturing to the French side if on a cruise ship. Getting back could be a problem unless one knows the strike is over or the exact location of any actions.