Thanks for all the good advice on this thread and others. I'm planning a similar jaunt for me and my family this summer - five of us: me, husband, three teens. Last year was our first tour all on solo bikes rather than tandems, and it went so well that we'd like to do more of that - which opens up getting trains and ferries to France...
But, living in East Anglia and having mainly used the super convenient Harwich-Hook of Holland ferry, I had no idea there were so many options for ferries to France! We've done Dover-Dunkirk before. Other than that, does anyone have any guidance about which ferry routes are better than any others?
(Where better means: easier to get bikes on and off, minimal sickness-inducing ferry, easier port negotiation(s), relatively convenient UK train. Cost important but happy to pay a bit more if it means less terror bike infrastructure - the advantage of tandems was less stress about hair-raising infrastructure)