WE are a family of 4 and we have never been to London or taken the Eurostar to Paris.
We have been to Paris but almost 15 years ago. The flight is cheaper by about $30pp (so $120 total). And the train is a longer trip. Is it worth it - the experience? Has it made anyone motion sick?
Where exactly are you let out in Paris - do you still need a cab into town or are you close enough to a metro station?