//Come next summer, while sitting in a car for 10 hours with screaming kids – waiting to board a ferry to Calais, you’ll remember this post and be thinking ‘this has nothing to do with Brexit’.//
If you've any sense and a situation prevails that is likely to lead to that, you wouldn't go anywhere near a ferry to France.
But of course we don't know whether such problems will prevail and until we do this is isle speculation:
"He said it could take 10 minutes to register one car carrying four people: two minutes per passenger and then two minutes for the vehicle."
But then:
"However, the port does not yet know what technology will be used and therefore exactly how long the process will take."