Hi,wiles9,
I road several parts of your tour.
About Bordeaux heading north: I would prefer the small Medoc roads west of Gironde river, Carcans --> Le-Verdon-sur-mer for example.
This is the best place for bathing I've ever seen (many of these villages have a "plage dependence").
There is a ferry from Le-Verdon-sur-mer to Royan (1 hour or so).

About pyrennees: If you like mountain climbing: that's bikers paradise, great views but steep. If you're a "flat lander": spanish car drivers don't seem to know what a bike is all about and there are not many small roads east --> west. I would thus prefer the french side (or via Vielha to Bagnères-de-Luchon)

marmotte