Biarritz route and stop over advice

We are staying at Pavillion Royal at the beginning of August and would really like some recommendations on the best route and stopover sites.

We're thinking of doing early morning  (8 am)Eurotunnel crossing  and want to arrive onsite on Tuesday. So either Sunday crossing and 2 night stop or Monday and 1 night stop.

I've Just done a quick AA route planner via Rouen and it suggests Rouen, Le Mans, Tours, Poitiers, Bordeaux.  I'm thinking this could potentially be very busy being August.  Which route do other members use?