Can anyone recommend the best route from the US? Should we fly to London or Paris and then fly to Marseille?
When I can't get a direct flight (which I usually can't), I prefer to end the first leg over here so as to crowd my first day in Europe with as little as possible.
The argument against this, I suppose, is to get across the pond as soon as possible--if the first leg is late or second leg is delayed, at least you are in Europe. But, my way I arrive with nothing else to do but leave the airport.
Based on what people have said about security and baggage restrictions at Heathrow, I would avoid changing planes in London unless checking my luggage.