Hi Rosalie - I do sympathise - in June we drove from Cumbria via Dover-Calais to St Gallen in eastern Switzerland in 2 days. OH and I shared the driving, but it was exhausting and stressful. I hated living out of a suitcase too!

To make the journey more bearable, do take plenty of CDS and make sure they are accessible. We once drove all the way from Beaune to Calais with just the Corrs to listen too! I do like the Corrs, but you can have too much of a good thing!
There are plenty of picnic areas on the French motorways, so make sure you take time to stop and rest. Oh - the tolls are pretty expensive, but you do make more progress than on the other roads.

We used to drive to OH's family home in southern Austria - but I really object to 5 days of my precious holiday being spent on the autobahn. So for the last two visit we've flown and hired a car from the airport. Perhaps when we retire ...... but only if we can take our time and stop off in interesting places.

Hope you can come to a reasonable compromise and enjoy your holiday!